(20170207)开源第三方学习之JSONModel
主要作用是把JSON字符串转成Model实体，也可以把实体转化成JSON字符串；还包含一些转字典的内容；JOSN字符串通过AFNetworking转化成字典，然后再能过字典跟实体进行转换；
2：原理实现：
主要介绍关于实体对象转换地原理，其它不在这个里面进行介绍；其主要还是运用运用时的机制，对属性进行获取换进行处理；
-(id)initWithDictionary:(NSDictionary*)dict error:(NSError**)err { //check for nil input //1.为空判断 if (!dict) { if (err) *err = [JSONModelError errorInputIsNil]; return nil; } //invalid input, just create empty instance //2.类型判断 if (![dict isKindOfClass:[NSDictionary class]]) { if (err) *err = [JSONModelError errorInvalidDataWithMessage:@"Attempt to initialize JSONModel object using initWithDictionary:error: but the dictionary parameter was not an 'NSDictionary'."]; return nil; } //create a class instance //3.核心，初始化映射property self = [self init]; if (!self) { //super init didn't succeed if (err) *err = [JSONModelError errorModelIsInvalid]; return nil; } //check incoming data structure //4.检查映射结构是否能够从dictionary中找到相应的数据 if (![self __doesDictionary:dict matchModelWithKeyMapper:self.__keyMapper error:err]) { return nil; } //import the data from a dictionary //5.进行数据赋值 if (![self __importDictionary:dict withKeyMapper:self.__keyMapper validation:YES error:err]) { return nil; } //run any custom model validation //6.本地数据检查 if (![self validate:err]) { return nil; } //model is valid! yay! return self; }
2.1：如何获得属性相关修饰符？采用运行时的机制，获取实体中的属性，并通过属性获取对应的修饰符；不同的字符跟符号代表不一样的修饰符；
代码：
unsigned int propertyCount; objc_property_t *properties = class_copyPropertyList(class, &propertyCount); //loop over the class properties for (unsigned int i = 0; i < propertyCount; i++) { JSONModelClassProperty* p = [[JSONModelClassProperty alloc] init]; //get property name objc_property_t property = properties[i]; const char *propertyName = property_getName(property); p.name = @(propertyName); //JMLog(@"property: %@", p.name); //get property attributes const char *attrs = property_getAttributes(property); NSString* propertyAttributes = @(attrs); NSArray* attributeItems = [propertyAttributes componentsSeparatedByString:@",”]; ……. }
property_getAttributes函数返回objc_property_attribute_t结构体列表，objc_property_attribute_t结构体包含name和value，常用的属性如下：
属性类型 name值：T value：变化
编码类型 name值：C(copy) &(strong) W(weak)空(assign) 等 value：无
非/原子性 name值：空(atomic) N(Nonatomic) value：无
变量名称 name值：V value：变化
使用property_getAttributes获得的描述是property_copyAttributeList能获取到的所有的name和value的总体描述，如 T@"NSDictionary",C,N,V_dict1
2.2 通过NSScanner用于在字符串中扫描指定的字符，尤其是把它们翻译/转换为数字和别的字符串。可以在创建NSScaner时指定它的string属性，然后scanner会按照你的要求从头到尾地扫描这个字符串的每个字符。
NSScanner* scanner = nil; scanner = [NSScanner scannerWithString: propertyAttributes]; //JMLog(@"attr: %@", [NSString stringWithCString:attrs encoding:NSUTF8StringEncoding]); [scanner scanUpToString:@"T" intoString: nil]; [scanner scanString:@"T" intoString:nil]; //check if the property is an instance of a class if ([scanner scanString:@"@\"" intoString: &propertyType]) { [scanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"\"<"] intoString:&propertyType]; //JMLog(@"type: %@", propertyClassName); p.type = NSClassFromString(propertyType); p.isMutable = ([propertyType rangeOfString:@"Mutable"].location != NSNotFound); p.isStandardJSONType = [allowedJSONTypes containsObject:p.type]; //read through the property protocols while ([scanner scanString:@"<" intoString:NULL]) { NSString* protocolName = nil; [scanner scanUpToString:@">" intoString: &protocolName]; if ([protocolName isEqualToString:@"Optional"]) { p.isOptional = YES; } else if([protocolName isEqualToString:@"Index"]) { p.isIndex = YES; objc_setAssociatedObject( self.class, &kIndexPropertyNameKey, p.name, OBJC_ASSOCIATION_RETAIN // This is atomic ); } else if([protocolName isEqualToString:@"ConvertOnDemand"]) { p.convertsOnDemand = YES; } else if([protocolName isEqualToString:@"Ignore"]) { p = nil; } else { p.protocol = protocolName; } [scanner scanString:@">" intoString:NULL]; } } //check if the property is a structure else if ([scanner scanString:@"{" intoString: &propertyType]) { [scanner scanCharactersFromSet:[NSCharacterSet alphanumericCharacterSet] intoString:&propertyType]; p.isStandardJSONType = NO; p.structName = propertyType; } //the property must be a primitive else { //the property contains a primitive data type [scanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@","] intoString:&propertyType]; //get the full name of the primitive type propertyType = valueTransformer.primitivesNames[propertyType]; if (![allowedPrimitiveTypes containsObject:propertyType]) { //type not allowed - programmer mistaked -> exception @throw [NSException exceptionWithName:@"JSONModelProperty type not allowed" reason:[NSString stringWithFormat:@"Property type of %@.%@ is not supported by JSONModel.", self.class, p.name] userInfo:nil]; } }
然后对符号的字符串进行解析分析，把相应的字符串获取到进行判断处理；对于有增加相应的属性进行操作，如忽略、可为空等，如是block修饰的也直接置空属性，不对它进行转换；代码如下：
NSString *nsPropertyName = @(propertyName); if([[self class] propertyIsOptional:nsPropertyName]){ p.isOptional = YES; } if([[self class] propertyIsIgnored:nsPropertyName]){ p = nil; } //few cases where JSONModel will ignore properties automatically if ([propertyType isEqualToString:@"Block"]) { p = nil; }
2.3 JSONModel关于keyMapper修改对应的属性对应名称
下面这段平时我们用于替换Model跟JSON字符串不一样的地方，重新给它命名一个属性新名字；
+(JSONKeyMapper*)keyMapper { return [[JSONKeyMapper alloc] initWithDictionary:@{ @"new_password": @"my_new_password", }]; }
其实是在JSONModel初始化过程中有对keyMapper进行一个判断处理；判断当前的实体对象中是否有这个方法，如果有且还没有被映射缓存过，则对它进行处理；
id mapper = [[self class] keyMapper]; if ( mapper && !objc_getAssociatedObject(self.class, &kMapperObjectKey) ) { objc_setAssociatedObject( self.class, &kMapperObjectKey, mapper, OBJC_ASSOCIATION_RETAIN // This is atomic ); }
其中关于&kClassPropertiesKey， &kMapperObjectKey的运用说明，是映射缓存的标识；
//使用AssociateObject进行映射property的缓存，判断是否映射过 if (!objc_getAssociatedObject(self.class, &kClassPropertiesKey)) { [self __inspectProperties]; } //同样使用AssociateObject进行映射property的缓存 if ( mapper && !objc_getAssociatedObject(self.class, &kMapperObjectKey) ) { }
写入标识的操作如下：
objc_setAssociatedObject( self.class, &kClassPropertiesKey, [propertyIndex copy], OBJC_ASSOCIATION_RETAIN // This is atomic );
2.4 关于健值是否缺少判断
获取到当前实体的属性值，对于那些可空的就不进行判断，也就没有放在下面这个NSMutableSet里面
-(NSMutableSet*)__requiredPropertyNames { //fetch the associated property names NSMutableSet* classRequiredPropertyNames = objc_getAssociatedObject(self.class, &kClassRequiredPropertyNamesKey); if (!classRequiredPropertyNames) { classRequiredPropertyNames = [NSMutableSet set]; [[self __properties__] enumerateObjectsUsingBlock:^(JSONModelClassProperty* p, NSUInteger idx, BOOL *stop) { if (!p.isOptional) [classRequiredPropertyNames addObject:p.name]; }]; //persist the list objc_setAssociatedObject( self.class, &kClassRequiredPropertyNamesKey, classRequiredPropertyNames, OBJC_ASSOCIATION_RETAIN // This is atomic ); } return classRequiredPropertyNames; }
这边要兼容除了dic字典里面的属性还要处理如果有KeyMapper的替换属性；然后进行统一判断；
-(BOOL)__doesDictionary:(NSDictionary*)dict matchModelWithKeyMapper:(JSONKeyMapper*)keyMapper error:(NSError**)err { //check if all required properties are present NSArray* incomingKeysArray = [dict allKeys]; NSMutableSet* requiredProperties = [self __requiredPropertyNames]; NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray]; //transform the key names, if neccessary if (keyMapper || globalKeyMapper) { NSMutableSet* transformedIncomingKeys = [NSMutableSet setWithCapacity: requiredProperties.count]; NSString* transformedName = nil; //loop over the required properties list for (JSONModelClassProperty* property in [self __properties__]) { transformedName = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper importing:YES] : property.name; //chek if exists and if so, add to incoming keys id value; @try { value = [dict valueForKeyPath:transformedName]; } @catch (NSException *exception) { value = dict[transformedName]; } if (value) { [transformedIncomingKeys addObject: property.name]; } } //overwrite the raw incoming list with the mapped key names incomingKeys = transformedIncomingKeys; } //check for missing input keys if (![requiredProperties isSubsetOfSet:incomingKeys]) { //get a list of the missing properties [requiredProperties minusSet:incomingKeys]; //not all required properties are in - invalid input JMLog(@"Incoming data was invalid [%@ initWithDictionary:]. Keys missing: %@", self.class, requiredProperties); if (err) *err = [JSONModelError errorInvalidDataWithMissingKeys:requiredProperties]; return NO; } //not needed anymore incomingKeys= nil; requiredProperties= nil; return YES; }
2.5 开始进行赋值操作
首先获取到对应的属性列表数组
-(NSArray*)__properties__ { //fetch the associated object NSDictionary* classProperties = objc_getAssociatedObject(self.class, &kClassPropertiesKey); if (classProperties) return [classProperties allValues]; //if here, the class needs to inspect itself [self __setup__]; //return the property list classProperties = objc_getAssociatedObject(self.class, &kClassPropertiesKey); return [classProperties allValues]; }
然后主要进行属性赋值
-(BOOL)__importDictionary:(NSDictionary*)dict withKeyMapper:(JSONKeyMapper*)keyMapper validation:(BOOL)validation error:(NSError**)err { //loop over the incoming keys and set self's properties //循环遍历映射出来的JSONModelClassProperty结构体 for (JSONModelClassProperty* property in [self __properties__]) { //convert key name ot model keys, if a mapper is provided //keyMapper映射，获取镇真正的值 NSString* jsonKeyPath = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper importing:YES] : property.name; //JMLog(@"keyPath: %@", jsonKeyPath); //general check for data type compliance id jsonValue; @try { jsonValue = [dict valueForKeyPath: jsonKeyPath]; } @catch (NSException *exception) { jsonValue = dict[jsonKeyPath]; } //check for Optional properties if (isNull(jsonValue)) { //skip this property, continue with next property if (property.isOptional || !validation) continue; if (err) { //null value for required property NSString* msg = [NSString stringWithFormat:@"Value of required model key %@ is null", property.name]; JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg]; *err = [dataErr errorByPrependingKeyPathComponent:property.name]; } return NO; } Class jsonValueClass = [jsonValue class]; BOOL isValueOfAllowedType = NO; //判断数据输入类型是不是允许的json类型 for (Class allowedType in allowedJSONTypes) { if ( [jsonValueClass isSubclassOfClass: allowedType] ) { isValueOfAllowedType = YES; break; } } if (isValueOfAllowedType==NO) { //type not allowed JMLog(@"Type %@ is not allowed in JSON.", NSStringFromClass(jsonValueClass)); if (err) { NSString* msg = [NSString stringWithFormat:@"Type %@ is not allowed in JSON.", NSStringFromClass(jsonValueClass)]; JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg]; *err = [dataErr errorByPrependingKeyPathComponent:property.name]; } return NO; } //check if there's matching property in the model if (property) { // check for custom setter, than the model doesn't need to do any guessing // how to read the property's value from JSON // 使用对象相应的setter方法进行set if ([self __customSetValue:jsonValue forProperty:property]) { //skip to next JSON key continue; }; // 0) handle primitives // 代表基础类型，比如int float等，直接使用kvc赋值 if (property.type == nil && property.structName==nil) { //generic setter if (jsonValue != [self valueForKey:property.name]) { [self setValue:jsonValue forKey: property.name]; } //skip directly to the next key continue; } // 0.5) handle nils if (isNull(jsonValue)) { if ([self valueForKey:property.name] != nil) { [self setValue:nil forKey: property.name]; } continue; } // 1) check if property is itself a JSONModel // 判断子结构是否是一个JSONModel结构，进行递归遍历，先将子结构遍历完并赋值完成 if ([self __isJSONModelSubClass:property.type]) { //initialize the property's model, store it JSONModelError* initErr = nil; id value = [[property.type alloc] initWithDictionary: jsonValue error:&initErr]; if (!value) { //skip this property, continue with next property if (property.isOptional || !validation) continue; // Propagate the error, including the property name as the key-path component if((err != nil) && (initErr != nil)) { *err = [initErr errorByPrependingKeyPathComponent:property.name]; } return NO; } if (![value isEqual:[self valueForKey:property.name]]) { [self setValue:value forKey: property.name]; } //for clarity, does the same without continue continue; } else { // 2) check if there's a protocol to the property // ) might or not be the case there's a built in transform for it // 是否包含protocol的字段，该字段主要用来表明array或者dictionary中的对象类型 if (property.protocol) { //JMLog(@"proto: %@", p.protocol); //循环遍历子内容，将对应的类型赋给相应的array或者dictionary jsonValue = [self __transform:jsonValue forProperty:property error:err]; if (!jsonValue) { if ((err != nil) && (*err == nil)) { NSString* msg = [NSString stringWithFormat:@"Failed to transform value, but no error was set during transformation. (%@)", property]; JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg]; *err = [dataErr errorByPrependingKeyPathComponent:property.name]; } return NO; } } // 3.1) handle matching standard JSON types // 判断标准的json类型，比如nsstring等 if (property.isStandardJSONType && [jsonValue isKindOfClass: property.type]) { //mutable properties if (property.isMutable) { jsonValue = [jsonValue mutableCopy]; } //set the property value if (![jsonValue isEqual:[self valueForKey:property.name]]) { [self setValue:jsonValue forKey: property.name]; } continue; } // 3.3) handle values to transform // 其他处理情况，主要是一些类型转换的情况，比如nsstring转换为nsurl等 if ( (![jsonValue isKindOfClass:property.type] && !isNull(jsonValue)) || //the property is mutable property.isMutable || //custom struct property property.structName ) { // searched around the web how to do this better // but did not find any solution, maybe that's the best idea? (hardly) // 获取真实的json数据类型 Class sourceClass = [JSONValueTransformer classByResolvingClusterClasses:[jsonValue class]]; //JMLog(@"to type: [%@] from type: [%@] transformer: [%@]", p.type, sourceClass, selectorName); //build a method selector for the property and json object classes // 通过property类型和json数据类型进行转换的判断 NSString* selectorName = [NSString stringWithFormat:@"%@From%@:", (property.structName? property.structName : property.type), //target name sourceClass]; //source name SEL selector = NSSelectorFromString(selectorName); //check for custom transformer //是否有本地转换的方法 BOOL foundCustomTransformer = NO; if ([valueTransformer respondsToSelector:selector]) { foundCustomTransformer = YES; } else { //try for hidden custom transformer selectorName = [NSString stringWithFormat:@"__%@",selectorName]; selector = NSSelectorFromString(selectorName); if ([valueTransformer respondsToSelector:selector]) { foundCustomTransformer = YES; } } //check if there's a transformer with that name if (foundCustomTransformer) { //it's OK, believe me... #pragma clang diagnostic push #pragma clang diagnostic ignored "-Warc-performSelector-leaks" //transform the value // 通过 JSONValueTransformer 进行类型转换 jsonValue = [valueTransformer performSelector:selector withObject:jsonValue]; #pragma clang diagnostic pop if (![jsonValue isEqual:[self valueForKey:property.name]]) { [self setValue:jsonValue forKey: property.name]; } } else { // it's not a JSON data type, and there's no transformer for it // if property type is not supported - that's a programmer mistake -> exception @throw [NSException exceptionWithName:@"Type not allowed" reason:[NSString stringWithFormat:@"%@ type not supported for %@.%@", property.type, [self class], property.name] userInfo:nil]; return NO; } } else { // 3.4) handle "all other" cases (if any) if (![jsonValue isEqual:[self valueForKey:property.name]]) { [self setValue:jsonValue forKey: property.name]; } } } } } return YES; }
其中获取到值对应的类型是否在支持的转化类型中
allowedJSONTypes = @[ [NSString class], [NSNumber class], [NSDecimalNumber class], [NSArray class], [NSDictionary class], [NSNull class], //immutable JSON classes [NSMutableString class], [NSMutableArray class], [NSMutableDictionary class] //mutable JSON classes ]; allowedPrimitiveTypes = @[ @"BOOL", @"float", @"int", @"long", @"double", @"short", //and some famous aliases @"NSInteger", @"NSUInteger", @"Block" ];
然后上面的代码用于下面进行判断
Class jsonValueClass = [jsonValue class]; BOOL isValueOfAllowedType = NO; for (Class allowedType in allowedJSONTypes) { if ( [jsonValueClass isSubclassOfClass: allowedType] ) { isValueOfAllowedType = YES; break; } }
2.6 定义空的协议用于区分一些属性标识
@protocol Ignore @end /** * Protocol for defining optional properties in a JSON Model class. Use like below to define * model properties that are not required to have values in the JSON input: * * @property (strong, nonatomic) NSString<Optional>* propertyName; * */ @protocol Optional @end /** * Protocol for defining index properties in a JSON Model class. Use like below to define * model properties that are considered the Model's identifier (id). * * @property (strong, nonatomic) NSString<Index>* propertyName; * */ @protocol Index @end //使所有对象可选兼容，避免编译器警告 @interface NSObject(JSONModelPropertyCompatibility)<Optional, Index, Ignore> @end
特别是Optional为可空的标识例如我们给一个属性设置可空时 @property (nonatomic, copy) NSString<Optional> *current_status;，然后在上面获取属性的字符串中关于是否存在这个标识字符串，做一些属性的配置；它是被包含在<>里面；
while ([scanner scanString:@"<" intoString:NULL]) { NSString* protocolName = nil; [scanner scanUpToString:@">" intoString: &protocolName]; if ([protocolName isEqualToString:@"Optional"]) { p.isOptional = YES; } else if([protocolName isEqualToString:@"Index"]) { #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wdeprecated-declarations" p.isIndex = YES; #pragma GCC diagnostic pop objc_setAssociatedObject( self.class, &kIndexPropertyNameKey, p.name, OBJC_ASSOCIATION_RETAIN // This is atomic ); } else if([protocolName isEqualToString:@"Ignore"]) { p = nil; } else { p.protocol = protocolName; } [scanner scanString:@">" intoString:NULL]; } }
3：关于属性类型的获取实例
定义一个类：
@interface MPAllModel : JSONModel @property(nonatomic,copy)NSString *name; @property(nonatomic,strong)NSString *userName; @property(nonatomic)int age; @property(nonatomic)float price; @property(nonatomic,strong)NSNumber *isShow; @property(nonatomic,assign)BOOL isError; @property(nonatomic,strong)NSArray *itemArray; @property(nonatomic,strong)NSArray<Optional> *dataArray; @end
然后利用运行时的代码，获得到这个类对应属性的字符串内容：
unsigned int outCount; int i; objc_property_t *property = class_copyPropertyList([MPAllModel class], &outCount); for (i = outCount -1; i >= 0 ; i--) { NSString *getPropertyName = [NSString stringWithCString:property_getName(property[i]) encoding:NSUTF8StringEncoding]; NSLog(@"getPropertyName: %@",getPropertyName); NSString *getPropertyNameString = [NSString stringWithCString:property_getAttributes(property[i]) encoding:NSUTF8StringEncoding]; NSLog(@"getPropertyNameString: %@",getPropertyNameString); }
得到下面对应的类型：
getPropertyName: dataArray getPropertyNameString: T@"NSArray<Optional>",&,N,V_dataArray getPropertyName: itemArray getPropertyNameString: T@"NSArray",&,N,V_itemArray getPropertyName: isError getPropertyNameString: TB,N,V_isError getPropertyName: isShow getPropertyNameString: T@"NSNumber",&,N,V_isShow getPropertyName: price getPropertyNameString: Tf,N,V_price getPropertyName: age getPropertyNameString: Ti,N,V_age getPropertyName: userName getPropertyNameString: T@"NSString",&,N,V_userName getPropertyName: name getPropertyNameString: T@"NSString",C,N,V_name
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