iOS进阶_KVC（&KVC赋值取值过程分析&KVC自定义&异常处理）

KVC（Key-value coding）

键值编码

基本使用

1. 能够对对象的私有成员进行取值赋值
2. 对数值和结构体型的属性进行的打包解包处理

实例：
WTPerson.h

#import <Foundation/Foundation.h>
 
@interface WTPerson : NSObject{
//    @public  //@protect默认
    NSString * _name;
}
 
/** name  **/
//@property(nonatomic,strong)NSString * name;
 
@end

ViewController.m　

#import "ViewController.h"
#import "WTPerson.h"
 
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *text;
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
    [super viewDidLoad];
    WTPerson * p = [WTPerson new];
    //访问成员变量
    //p.name = @"wt";
    //NSLog(@"%@",p.name);
 
    //访问私有变量（必须要要设置为public才可访问）
    //p->_name = @"wt";
    //NSLog(@"%@",p->_name);
 
    //KVC(即使不用public修饰，也可以访问私有变量)
    [p setValue:@"wt" forKey:@"name"];
    NSLog(@"%@",[p valueForKey:@"name"]);
 
    [self.text setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
}

KVC赋值取值过程分析和自定义及异常处理

赋值过程

• 1、先找相关方法set<Key>; _set<Key>; setIs<Key>;
• 2、若是没有相关方法+(BOOL)accessInstanceVariablesDirectly判断是否可以直接访问成员变量
• 3、如果判断NO，直接执行KVC的setValue:forUndefinedKey:(系统抛出一个异常，未定义key)
• 4、如果是YES，继续找相关变量_<key> _is<Key> <key> is<Key>
• 5、方法或成员都不存在，setValue:forUndefinedKey:方法默认是抛出异常

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实例验证

WTPerson.h

#import <Foundation/Foundation.h>
@interface WTPerson : NSObject{
    @public  //@protect默认
    NSString * _name;
    NSString * _isName;
    NSString * name;
    NSString * isName;
}
@end

WTPerson.m

#import "WTPerson.h"
@implementation WTPerson
 
-(void)setName:(NSString *)name{
    NSLog(@"%s",__func__);
}
 
-(void)_setName:(NSString *)name{
    NSLog(@"%s",__func__);
}
 
-(void)setIsName:(NSString *)name{
    NSLog(@"%s",__func__);
}
@end

ViewController.m

#import "ViewController.h"
#import "WTPerson.h"
 
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    WTPerson * p = [WTPerson new]; 
    //验证KVC赋值过程
    [p setValue:@"wt" forKey:@"name"];
 
    NSLog(@"name = %@",p->name);
    NSLog(@"_name = %@",p->_name);
    NSLog(@"isname = %@",p->isName);
    NSLog(@"_isname = %@",p->_isName);
}
 
@end

• 运行程序，我们把WTPerson.m中的-(void)setName:(NSString *)name、-(void)_setName:(NSString *)name、-(void)setIsName:(NSString *)name三个方法依次注释，我们发现三个方法都会被依次执行。

• 然后我们把WTPerson.h中的NSString * _name;、NSString * _isName;、NSString * name;、NSString * isName;依次注释，我们会发现4个属性依次被赋值。

在WTPerson.m中我们让accessInstanceVariablesDirectly返回NO，则程序直接崩溃。

+ (BOOL)accessInstanceVariablesDirectly{
    return NO;
}

　　取值过程

• 1、先找相关方法get<Key>,key
• 2、若没有相关方法，+(BOOL)accessInstanceVariabkesDirectly判断是否可以直接访问成员变量
• 3、如果是NO，直接执行KVC的valueForUndefinedKey:(系统抛出一个异常，未定义key)
• 4、如果是YES，继续找相关变量_<key>、_is<Key>、<key>、is<Key>
• 5、方法或成员都不存在，valueForUndefineKey:方法，默认是抛出异常

实例验证

WTPerson.m

#import "WTPerson.h"
 
@implementation WTPerson
 
//- (NSString*) getName{
//    NSLog(@"%s",__func__);
//    return @"getName";
//}
 
- (NSString*) name {
    return @"name";
}
 
//+ (BOOL)accessInstanceVariablesDirectly{
//    return NO;
//}
@end

ViewController.m

#import "ViewController.h"
#import "WTPerson.h"
 
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *text;
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
    [super viewDidLoad];
    WTPerson * p = [WTPerson new];
 
    //验证KVC取值过程
    NSLog(@"name = %@",[p valueForKey:@"name"]);
}
 
@end

取值方式与赋值方式大致相同。

KVC自定义

自定义KVC代码实现

创建分类NSObject+KVC

NSObject+KVC.h

#import <Foundation/Foundation.h>
 
@interface NSObject (KVC)
 
- (void)wt_setValue:(nullable id)value forKey:(NSString *)key;
 
- (id)wt_valueForKey:(NSString *)key;
 
@end

NSObject+KVC.m

#import "NSObject+KVC.h"
#import <objc/runtime.h>
 
@implementation NSObject (KVC)
 
- (id)wt_valueForKey:(NSString *)key{
    //判断是否合法
    if (key == nil && key.length ==0) {
        return nil;
    }
 
    //Key
    NSString * Key = key.capitalizedString;
 
    //先找相关方法 get<Key>,key
    NSString * getKey = [NSString stringWithFormat:@"get%@:",Key];
 
    if ([self respondsToSelector:NSSelectorFromString(getKey)]) {
        return [self performSelector:NSSelectorFromString(getKey)];
    }
 
    if ([self respondsToSelector:NSSelectorFromString(key)]) {
        return [self performSelector:NSSelectorFromString(key)];
    }
 
    if (![self.class accessInstanceVariablesDirectly]) {
        NSException * exception = [NSException exceptionWithName:@"NSUnknownKeyException" reason:@"setValue:forUndefineKey" userInfo:nil];
        @throw exception;
    }
 
    //再找相关变量
    //获取所有的成员变量
    unsigned int count = 0;
    Ivar * ivars = class_copyIvarList([self class], &count);
    NSMutableArray * arr = [[NSMutableArray alloc]init];
    for (int i = 0; i<count; i++) {
        Ivar var = ivars[i];
        const char * varName = ivar_getName(var);
        NSString *name = [NSString stringWithUTF8String:varName];
        [arr addObject:name];
    }
 
    //_<key> _is<Key> <key> is<Key>
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"_%@",key]]) {
 
            return object_getIvar(self, ivars[i]);
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"_is%@",Key]]) {
 
            return object_getIvar(self, ivars[i]);
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"%@",key]]) {
 
            return object_getIvar(self, ivars[i]);
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"is%@",Key]]) {
            return object_getIvar(self, ivars[i]);
        }
    }
    free(ivars);
    return nil;
}
 
- (void)wt_setValue:(nullable id)value forKey:(NSString *)key{
 
    //判断是否合法
    if (key == nil && key.length ==0) {
        return;
    }
 
    //Key
    NSString * Key = key.capitalizedString;
 
    //先找相关方法 set<Key>; _set<Key>; setIs<Key>;
    NSString * setKey = [NSString stringWithFormat:@"set%@:",Key];
 
    if ([self respondsToSelector:NSSelectorFromString(setKey)]) {
        [self performSelector:NSSelectorFromString(setKey) withObject:value];
        return;
    }
 
    NSString * _setKey = [NSString stringWithFormat:@"_set%@:",Key];
 
    if ([self respondsToSelector:NSSelectorFromString(_setKey)]) {
        [self performSelector:NSSelectorFromString(_setKey) withObject:value];
        return;
    }
 
    NSString * setIsKey = [NSString stringWithFormat:@"setIs%@:",Key];
    if ([self respondsToSelector:NSSelectorFromString(setIsKey)]) {
        [self performSelector:NSSelectorFromString(setIsKey) withObject:value];
        return;
    }
 
    if (![self.class accessInstanceVariablesDirectly]) {
        NSException * exception = [NSException exceptionWithName:@"NSUnknownKeyException" reason:@"setValue:forUndefineKey" userInfo:nil];
        @throw exception;
    }
 
    //再找相关变量
    //获取所有的成员变量
    unsigned int count = 0;
    Ivar * ivars = class_copyIvarList([self class], &count);
    NSMutableArray * arr = [[NSMutableArray alloc]init];
    for (int i = 0; i<count; i++) {
        Ivar var = ivars[i];
        const char * varName = ivar_getName(var);
        NSString *name = [NSString stringWithUTF8String:varName];
        [arr addObject:name];
    }
 
    //_<key> _is<Key> <key> is<Key>
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"_%@",key]]) {
            object_setIvar(self, ivars[i], value);
            free(ivars);
            return;
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"_is%@",Key]]) {
            object_setIvar(self, ivars[i], value);
            free(ivars);
            return;
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"%@",key]]) {
            object_setIvar(self, ivars[i], value);
            free(ivars);
            return;
        }
    }
 
    for (int i = 0; i < count; i++) {
        NSString *keyName = arr[i];
        if ([keyName isEqualToString:[NSString stringWithFormat:@"is%@",Key]]) {
            object_setIvar(self, ivars[i], value);
            free(ivars);
            return;
        }
    }
 
    [self setValue:value forUndefinedKey:Key];
    free(ivars);
}
@end

验证

ViewController.m

#import "ViewController.h"
#import "WTPerson.h"
#import "NSObject+KVC.h"
 
@interface ViewController ()
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
    [super viewDidLoad];
 
    WTPerson * p =[WTPerson new];
    [p wt_setValue:@"wt" forKey:@"name"];
 
    NSLog(@"name-KVC = %@",[p wt_valueForKey:@"name"]);
    NSLog(@"_name = %@",p->_name);
    NSLog(@"_isName = %@",p->_isName);
    NSLog(@"name = %@",p->name);
    NSLog(@"isName = %@",p->isName);
}
@end

　　在项目中

commond+shift+o 搜索setValue:forKey发现在Foundation框架下的NSKeyValueCoding文件下

 

 

 

我们查看这个文件中的方法，发现这个文件中是一些分类的集合

 

 

 

KVC异常处理及正确性验证

KVC异常处理

• 1、赋值为空 setNilValueForKey
• 2、Key值不存在 setValue:forUndefinedKey

正确性验证

validateValue
该方法的工作原理：

• 1、先找一下你的类中是否实现了方法 -(BOOL)validate<Key>:error;
• 2、如果实现了就会根据实现方法里面的自定义逻辑返回NO或者YES；如果没有实现这个方法，则系统默认返回YES

示例代码

WTPerson…h

#import <Foundation/Foundation.h>
 
@interface WTPerson : NSObject
 
/** name  **/
@property(nonatomic,strong)NSString * name;
 
/** age  **/
@property(nonatomic,assign)int age;
 
@end

WTPerson.m

#import "WTPerson.h"
 
@implementation WTPerson
 
//对非对象类型，值不能为空
- (void) setNilValueForKey:(NSString *)key{
    NSLog(@"%@ 值不能为空",key);
}
 
//赋值的key不存在
- (void) setValue:(id)value forUndefinedKey:(NSString *)key{
    NSLog(@"key = %@值不存在",key);
}
 
//取值的key不存在
- (id) valueForUndefinedKey:(NSString *)key{
    NSLog(@"key = %@值不存在",key);
    return nil;
}
 
//正确性验证
- (BOOL) validateAge:(inout id  _Nullable __autoreleasing *)ioValue error:(out NSError * _Nullable __autoreleasing *)outError{
    NSNumber* value = (NSNumber*)*ioValue;
    NSLog(@"%@",value);
    if ([value integerValue] >= 0 && [value integerValue] <= 200) {
        return YES;
    }
    return NO;
}
 
@end

ViewController.m

#import "ViewController.h"
#import "WTPerson.h"
#import "WTContainer.h"
 
@interface ViewController ()
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
    [super viewDidLoad];
    WTPerson * p = [WTPerson new];
 
    //异常处理
    [p setValue:@18 forKey:@"name"];
    [p setValue:nil forKey:@"name"];
    NSLog(@"name = %@",p.name);
 
    [p setValue:nil forKey:@"age"];
    NSLog(@"age = %d",p.age);
 
    [p setValue:@"hello" forKey:@"name1"];
 
    NSLog(@"name = %@",[p valueForKey:@"name1"]);
 
    //万能容器
    WTContainer * container = [WTContainer new];
 
    [container setValue:@"wt" forKey:@"name"];
    [container setValue:@18 forKey:@"age"];
 
    NSLog(@"name = %@,age = %@",[container valueForKey:@"name"],[container valueForKey:@"age"]);
 
    //正确性验证
    NSNumber * value = @200;
    NSNumber * value1 = @199;
 
    if ([p validateValue:&value1 forKey:@"age" error:NULL]) {
 
        [p setValue:value1 forKey:@"age"];
    }
 
    NSLog(@"%@",[p valueForKey:@"age"]);
}
 
@end

　　

1.  
   #import <Foundation/Foundation.h>
2.  
    
3.  
   @interface WTPerson : NSObject{
4.  
   // @public //@protect默认
5.  
   NSString * _name;
6.  
   }
7.  
    
8.  
   /** name **/
9.  
   //@property(nonatomic,strong)NSString * name;
10.  
     
11.  
    @end
12.  
    复制代码

ViewController.m

1.  
   #import "ViewController.h"
2.  
   #import "WTPerson.h"
3.  
    
4.  
   @interface ViewController ()
5.  
   @property (weak, nonatomic) IBOutlet UITextField *text;
6.  
    
7.  
   @end
8.  
    
9.  
   @implementation ViewController
10.  
     
11.  
    - (void)viewDidLoad {
12.  
    [super viewDidLoad];
13.  
    WTPerson * p = [WTPerson new];
14.  
    //访问成员变量
15.  
    //p.name = @"wt";
16.  
    //NSLog(@"%@",p.name);
17.  
     
18.  
    //访问私有变量（必须要要设置为public才可访问）
19.  
    //p->_name = @"wt";
20.  
    //NSLog(@"%@",p->_name);
21.  
     
22.  
    //KVC(即使不用public修饰，也可以访问私有变量)
23.  
    [p setValue:@"wt" forKey:@"name"];
24.  
    NSLog(@"%@",[p valueForKey:@"name"]);
25.  
     
26.  
    [self.text setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
27.  
    }
28.  
    复制代码

 

KVC赋值取值过程分析和自定义及异常处理

赋值过程

• 1、先找相关方法set<Key>; _set<Key>; setIs<Key>;
• 2、若是没有相关方法+(BOOL)accessInstanceVariablesDirectly判断是否可以直接访问成员变量
• 3、如果判断NO，直接执行KVC的setValue:forUndefinedKey:(系统抛出一个异常，未定义key)
• 4、如果是YES，继续找相关变量_<key> _is<Key> <key> is<Key>
• 5、方法或成员都不存在，setValue:forUndefinedKey:方法默认是抛出异常

实例验证

WTPerson.h

1.  
   #import <Foundation/Foundation.h>
2.  
   @interface WTPerson : NSObject{
3.  
   @public //@protect默认
4.  
   NSString * _name;
5.  
   NSString * _isName;
6.  
   NSString * name;
7.  
   NSString * isName;
8.  
   }
9.  
   @end
10.  
    复制代码

WTPerson.m

1.  
   #import "WTPerson.h"
2.  
   @implementation WTPerson
3.  
    
4.  
   -(void)setName:(NSString *)name{
5.  
   NSLog(@"%s",__func__);
6.  
   }
7.  
    
8.  
   -(void)_setName:(NSString *)name{
9.  
   NSLog(@"%s",__func__);
10.  
    }
11.  
     
12.  
    -(void)setIsName:(NSString *)name{
13.  
    NSLog(@"%s",__func__);
14.  
    }
15.  
    @end
16.  
    复制代码

ViewController.m

1.  
   #import "ViewController.h"
2.  
   #import "WTPerson.h"
3.  
    
4.  
   @interface ViewController ()
5.  
   @end
6.  
   @implementation ViewController
7.  
   - (void)viewDidLoad {
8.  
   [super viewDidLoad];
9.  
   WTPerson * p = [WTPerson new];
10.  
    //验证KVC赋值过程
11.  
    [p setValue:@"wt" forKey:@"name"];
12.  
     
13.  
    NSLog(@"name = %@",p->name);
14.  
    NSLog(@"_name = %@",p->_name);
15.  
    NSLog(@"isname = %@",p->isName);
16.  
    NSLog(@"_isname = %@",p->_isName);
17.  
    }
18.  
     
19.  
    @end
20.  
    复制代码

• 运行程序，我们把WTPerson.m中的-(void)setName:(NSString *)name、-(void)_setName:(NSString *)name、-(void)setIsName:(NSString *)name三个方法依次注释，我们发现三个方法都会被依次执行。

• 然后我们把WTPerson.h中的NSString * _name;、NSString * _isName;、NSString * name;、NSString * isName;依次注释，我们会发现4个属性依次被赋值。

在WTPerson.m中我们让accessInstanceVariablesDirectly返回NO，则程序直接崩溃。

1.  
   + (BOOL)accessInstanceVariablesDirectly{
2.  
   return NO;
3.  
   }
4.  
   复制代码

取值过程

• 1、先找相关方法get<Key>,key
• 2、若没有相关方法，+(BOOL)accessInstanceVariabkesDirectly判断是否可以直接访问成员变量
• 3、如果是NO，直接执行KVC的valueForUndefinedKey:(系统抛出一个异常，未定义key)
• 4、如果是YES，继续找相关变量_<key>、_is<Key>、<key>、is<Key>
• 5、方法或成员都不存在，valueForUndefineKey:方法，默认是抛出异常

实例验证

WTPerson.m

1.  
   #import "WTPerson.h"
2.  
    
3.  
   @implementation WTPerson
4.  
    
5.  
   //- (NSString*) getName{
6.  
   // NSLog(@"%s",__func__);
7.  
   // return @"getName";
8.  
   //}
9.  
    
10.  
    - (NSString*) name {
11.  
    return @"name";
12.  
    }
13.  
     
14.  
    //+ (BOOL)accessInstanceVariablesDirectly{
15.  
    // return NO;
16.  
    //}
17.  
    @end
18.  
    复制代码

ViewController.m

1.  
   #import "ViewController.h"
2.  
   #import "WTPerson.h"
3.  
    
4.  
   @interface ViewController ()
5.  
   @property (weak, nonatomic) IBOutlet UITextField *text;
6.  
    
7.  
   @end
8.  
    
9.  
   @implementation ViewController
10.  
     
11.  
    - (void)viewDidLoad {
12.  
    [super viewDidLoad];
13.  
    WTPerson * p = [WTPerson new];
14.  
     
15.  
    //验证KVC取值过程
16.  
    NSLog(@"name = %@",[p valueForKey:@"name"]);
17.  
    }
18.  
     
19.  
    @end
20.  
    复制代码

取值方式与赋值方式大致相同。

KVC自定义

自定义KVC代码实现

创建分类NSObject+KVC

NSObject+KVC.h

1.  
   #import <Foundation/Foundation.h>
2.  
    
3.  
   @interface NSObject (KVC)
4.  
    
5.  
   - (void)wt_setValue:(nullable id)value forKey:(NSString *)key;
6.  
    
7.  
   - (id)wt_valueForKey:(NSString *)key;
8.  
    
9.  
   @end
10.  
    复制代码

NSObject+KVC.m

1.  
   #import "NSObject+KVC.h"
2.  
   #import <objc/runtime.h>
3.  
    
4.  
   @implementation NSObject (KVC)
5.  
    
6.  
   - (id)wt_valueForKey:(NSString *)key{
7.  
   //判断是否合法
8.  
   if (key == nil && key.length ==0) {
9.  
   return nil;
10.  
    }
11.  
     
12.  
    //Key
13.  
    NSString * Key = key.capitalizedString;
14.  
     
15.  
    //先找相关方法 get<Key>,key
16.  
    NSString * getKey = [NSString stringWithFormat:@"get%@:",Key];
17.  
     
18.  
    if ([self respondsToSelector:NSSelectorFromString(getKey)]) {
19.  
    return [self performSelector:NSSelectorFromString(getKey)];
20.  
    }
21.  
     
22.  
    if ([self respondsToSelector:NSSelectorFromString(key)]) {
23.  
    return [self performSelector:NSSelectorFromString(key)];
24.  
    }
25.  
     
26.  
    if (![self.class accessInstanceVariablesDirectly]) {
27.  
    NSException * exception = [NSException exceptionWithName:@"NSUnknownKeyException" reason:@"setValue:forUndefineKey" userInfo:nil];
28.  
    @throw exception;
29.  
    }
30.  
     
31.  
    //再找相关变量
32.  
    //获取所有的成员变量
33.  
    unsigned int count = 0;
34.  
    Ivar * ivars = class_copyIvarList([self class], &count);
35.  
    NSMutableArray * arr = [[NSMutableArray alloc]init];
36.  
    for (int i = 0; i<count; i++) {
37.  
    Ivar var = ivars[i];
38.  
    const char * varName = ivar_getName(var);
39.  
    NSString *name = [NSString stringWithUTF8String:varName];
40.  
    [arr addObject:name];
41.  
    }
42.  
     
43.  
    //_<key> _is<Key> <key> is<Key>
44.  
    for (int i = 0; i < count; i++) {
45.  
    NSString *keyName = arr[i];
46.  
    if ([keyName isEqualToString:[NSString stringWithFormat:@"_%@",key]]) {
47.  
     
48.  
    return object_getIvar(self, ivars[i]);
49.  
    }
50.  
    }
51.  
     
52.  
    for (int i = 0; i < count; i++) {
53.  
    NSString *keyName = arr[i];
54.  
    if ([keyName isEqualToString:[NSString stringWithFormat:@"_is%@",Key]]) {
55.  
     
56.  
    return object_getIvar(self, ivars[i]);
57.  
    }
58.  
    }
59.  
     
60.  
    for (int i = 0; i < count; i++) {
61.  
    NSString *keyName = arr[i];
62.  
    if ([keyName isEqualToString:[NSString stringWithFormat:@"%@",key]]) {
63.  
     
64.  
    return object_getIvar(self, ivars[i]);
65.  
    }
66.  
    }
67.  
     
68.  
    for (int i = 0; i < count; i++) {
69.  
    NSString *keyName = arr[i];
70.  
    if ([keyName isEqualToString:[NSString stringWithFormat:@"is%@",Key]]) {
71.  
    return object_getIvar(self, ivars[i]);
72.  
    }
73.  
    }
74.  
    free(ivars);
75.  
    return nil;
76.  
    }
77.  
     
78.  
    - (void)wt_setValue:(nullable id)value forKey:(NSString *)key{
79.  
     
80.  
    //判断是否合法
81.  
    if (key == nil && key.length ==0) {
82.  
    return;
83.  
    }
84.  
     
85.  
    //Key
86.  
    NSString * Key = key.capitalizedString;
87.  
     
88.  
    //先找相关方法 set<Key>; _set<Key>; setIs<Key>;
89.  
    NSString * setKey = [NSString stringWithFormat:@"set%@:",Key];
90.  
     
91.  
    if ([self respondsToSelector:NSSelectorFromString(setKey)]) {
92.  
    [self performSelector:NSSelectorFromString(setKey) withObject:value];
93.  
    return;
94.  
    }
95.  
     
96.  
    NSString * _setKey = [NSString stringWithFormat:@"_set%@:",Key];
97.  
     
98.  
    if ([self respondsToSelector:NSSelectorFromString(_setKey)]) {
99.  
    [self performSelector:NSSelectorFromString(_setKey) withObject:value];
100.  
     return;
101.  
     }
102.  
      
103.  
     NSString * setIsKey = [NSString stringWithFormat:@"setIs%@:",Key];
104.  
     if ([self respondsToSelector:NSSelectorFromString(setIsKey)]) {
105.  
     [self performSelector:NSSelectorFromString(setIsKey) withObject:value];
106.  
     return;
107.  
     }
108.  
      
109.  
     if (![self.class accessInstanceVariablesDirectly]) {
110.  
     NSException * exception = [NSException exceptionWithName:@"NSUnknownKeyException" reason:@"setValue:forUndefineKey" userInfo:nil];
111.  
     @throw exception;
112.  
     }
113.  
      
114.  
     //再找相关变量
115.  
     //获取所有的成员变量
116.  
     unsigned int count = 0;
117.  
     Ivar * ivars = class_copyIvarList([self class], &count);
118.  
     NSMutableArray * arr = [[NSMutableArray alloc]init];
119.  
     for (int i = 0; i<count; i++) {
120.  
     Ivar var = ivars[i];
121.  
     const char * varName = ivar_getName(var);
122.  
     NSString *name = [NSString stringWithUTF8String:varName];
123.  
     [arr addObject:name];
124.  
     }
125.  
      
126.  
     //_<key> _is<Key> <key> is<Key>
127.  
     for (int i = 0; i < count; i++) {
128.  
     NSString *keyName = arr[i];
129.  
     if ([keyName isEqualToString:[NSString stringWithFormat:@"_%@",key]]) {
130.  
     object_setIvar(self, ivars[i], value);
131.  
     free(ivars);
132.  
     return;
133.  
     }
134.  
     }
135.  
      
136.  
     for (int i = 0; i < count; i++) {
137.  
     NSString *keyName = arr[i];
138.  
     if ([keyName isEqualToString:[NSString stringWithFormat:@"_is%@",Key]]) {
139.  
     object_setIvar(self, ivars[i], value);
140.  
     free(ivars);
141.  
     return;
142.  
     }
143.  
     }
144.  
      
145.  
     for (int i = 0; i < count; i++) {
146.  
     NSString *keyName = arr[i];
147.  
     if ([keyName isEqualToString:[NSString stringWithFormat:@"%@",key]]) {
148.  
     object_setIvar(self, ivars[i], value);
149.  
     free(ivars);
150.  
     return;
151.  
     }
152.  
     }
153.  
      
154.  
     for (int i = 0; i < count; i++) {
155.  
     NSString *keyName = arr[i];
156.  
     if ([keyName isEqualToString:[NSString stringWithFormat:@"is%@",Key]]) {
157.  
     object_setIvar(self, ivars[i], value);
158.  
     free(ivars);
159.  
     return;
160.  
     }
161.  
     }
162.  
      
163.  
     [self setValue:value forUndefinedKey:Key];
164.  
     free(ivars);
165.  
     }
166.  
     @end
167.  
     复制代码

验证

ViewController.m

1.  
   #import "ViewController.h"
2.  
   #import "WTPerson.h"
3.  
   #import "NSObject+KVC.h"
4.  
    
5.  
   @interface ViewController ()
6.  
    
7.  
   @end
8.  
    
9.  
   @implementation ViewController
10.  
     
11.  
    - (void)viewDidLoad {
12.  
    [super viewDidLoad];
13.  
     
14.  
    WTPerson * p =[WTPerson new];
15.  
    [p wt_setValue:@"wt" forKey:@"name"];
16.  
     
17.  
    NSLog(@"name-KVC = %@",[p wt_valueForKey:@"name"]);
18.  
    NSLog(@"_name = %@",p->_name);
19.  
    NSLog(@"_isName = %@",p->_isName);
20.  
    NSLog(@"name = %@",p->name);
21.  
    NSLog(@"isName = %@",p->isName);
22.  
    }
23.  
    @end
24.  
    复制代码

在项目中
commond+shift+o 搜索setValue:forKey发现在Foundation框架下的NSKeyValueCoding文件下

 

 

 

我们查看这个文件中的方法，发现这个文件中是一些分类的集合

 

 

 

KVC异常处理及正确性验证

KVC异常处理

• 1、赋值为空 setNilValueForKey
• 2、Key值不存在 setValue:forUndefinedKey

正确性验证

validateValue
该方法的工作原理：

• 1、先找一下你的类中是否实现了方法 -(BOOL)validate<Key>:error;
• 2、如果实现了就会根据实现方法里面的自定义逻辑返回NO或者YES；如果没有实现这个方法，则系统默认返回YES

示例代码

WTPerson…h

1.  
   #import <Foundation/Foundation.h>
2.  
    
3.  
   @interface WTPerson : NSObject
4.  
    
5.  
   /** name **/
6.  
   @property(nonatomic,strong)NSString * name;
7.  
    
8.  
   /** age **/
9.  
   @property(nonatomic,assign)int age;
10.  
     
11.  
    @end
12.  
    复制代码

WTPerson.m

1.  
   #import "WTPerson.h"
2.  
    
3.  
   @implementation WTPerson
4.  
    
5.  
   //对非对象类型，值不能为空
6.  
   - (void) setNilValueForKey:(NSString *)key{
7.  
   NSLog(@"%@ 值不能为空",key);
8.  
   }
9.  
    
10.  
    //赋值的key不存在
11.  
    - (void) setValue:(id)value forUndefinedKey:(NSString *)key{
12.  
    NSLog(@"key = %@值不存在",key);
13.  
    }
14.  
     
15.  
    //取值的key不存在
16.  
    - (id) valueForUndefinedKey:(NSString *)key{
17.  
    NSLog(@"key = %@值不存在",key);
18.  
    return nil;
19.  
    }
20.  
     
21.  
    //正确性验证
22.  
    - (BOOL) validateAge:(inout id _Nullable __autoreleasing *)ioValue error:(out NSError * _Nullable __autoreleasing *)outError{
23.  
    NSNumber* value = (NSNumber*)*ioValue;
24.  
    NSLog(@"%@",value);
25.  
    if ([value integerValue] >= 0 && [value integerValue] <= 200) {
26.  
    return YES;
27.  
    }
28.  
    return NO;
29.  
    }
30.  
     
31.  
    @end
32.  
    复制代码

ViewController.m

1.  
   #import "ViewController.h"
2.  
   #import "WTPerson.h"
3.  
   #import "WTContainer.h"
4.  
    
5.  
   @interface ViewController ()
6.  
    
7.  
   @end
8.  
    
9.  
   @implementation ViewController
10.  
     
11.  
    - (void)viewDidLoad {
12.  
    [super viewDidLoad];
13.  
    WTPerson * p = [WTPerson new];
14.  
     
15.  
    //异常处理
16.  
    [p setValue:@18 forKey:@"name"];
17.  
    [p setValue:nil forKey:@"name"];
18.  
    NSLog(@"name = %@",p.name);
19.  
     
20.  
    [p setValue:nil forKey:@"age"];
21.  
    NSLog(@"age = %d",p.age);
22.  
     
23.  
    [p setValue:@"hello" forKey:@"name1"];
24.  
     
25.  
    NSLog(@"name = %@",[p valueForKey:@"name1"]);
26.  
     
27.  
    //万能容器
28.  
    WTContainer * container = [WTContainer new];
29.  
     
30.  
    [container setValue:@"wt" forKey:@"name"];
31.  
    [container setValue:@18 forKey:@"age"];
32.  
     
33.  
    NSLog(@"name = %@,age = %@",[container valueForKey:@"name"],[container valueForKey:@"age"]);
34.  
     
35.  
    //正确性验证
36.  
    NSNumber * value = @200;
37.  
    NSNumber * value1 = @199;
38.  
     
39.  
    if ([p validateValue:&value1 forKey:@"age" error:NULL]) {
40.  
     
41.  
    [p setValue:value1 forKey:@"age"];
42.  
    }
43.  
     
44.  
    NSLog(@"%@",[p valueForKey:@"age"]);
45.  
    }
46.  
     
47.  
    @end

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