KVC取值的常用几种骚操作

取纯数字数组中的最小值,最大值和平均值,求和

     NSArray<NSNumber*> *numbers = @[@(2.0),@(3.5),@(99.0),@(6.66),@(10.0)];
    
     NSArray<NSString*> *numberStrArr = @[@"2.0",@"3.5",@"99.0",@"6.66",@"10.0"];

    //最小值
    CGFloat minNumber = [[numbers valueForKeyPath:@"@min.doubleValue"] doubleValue];
    NSLog(@"minNumber: %.2f",minNumber);
    NSString *minStr = [[numberStrArr valueForKeyPath:@"@min.floatValue"] stringValue];
    NSLog(@"minStr: %@",minStr);

    //最大值
    NSInteger maxNumber = [[numbers valueForKeyPath:@"@max.integerValue"] integerValue];
    NSLog(@"maxNumber: %ld",maxNumber);
    NSString *maxNumberStr = [[numbers valueForKeyPath:@"@max.integerValue"] stringValue];
    NSLog(@"maxNumberStr: %@",maxNumberStr);

     //平均值
    NSString *avgNumber = [[numbers valueForKeyPath:@"@avg.doubleValue"] stringValue];
    NSLog(@"avgNumber: %@",avgNumber);
    NSString *avgNumberStr = [[numbers valueForKeyPath:@"@avg.doubleValue"] stringValue];
    NSLog(@"avgNumberStr: %@",avgNumberStr);

    //求和
    CGFloat sum = [[numbers valueForKeyPath:@"@sum.floatValue"] floatValue];
    //NSLog(@"sum: %.2f",sum);

    NSArray<NSNumber*> *numbers001 = @[@(2.0),@(2.0),@(99.0),@(6.66),@(6.66)];
    //去重生成新的数组
    NSArray<NSNumber*> *newNumbers = [numbers001 valueForKeyPath:@"@distinctUnionOfObjects.floatValue"];
   // NSLog(@"newNumbers: %@",newNumbers);

    NSArray *numbers002 = @[@(2.22),@(2.22),@(99.99),@(6.66),@(6.66)];
    //与distinctUnionOfObjects去重相反 生成指定条件全新的数组
    NSArray *newNumbers = [numbers002 valueForKeyPath:@"@unionOfObjects.stringValue"];
    //NSLog(@"newNumbers: %@",newNumbers);

//控制台打印如下:     
    minNumber: 2.00
    minStr: 2
   
    maxNumber: 99
    maxNumberStr: 99
    
    avgNumber: 24.232
    avgNumberStr: 24.232

数组内部元素类型转换

    NSArray<NSNumber*> *numbers = @[@(2.0),@(3.5),@(99.0),@(6.66),@(10.0)];
      
    //[NSNumber]数组转为[NSString]数组
    NSArray<NSString*> *stringArray = [numbers valueForKeyPath:@"intValue.stringValue"];
    NSLog(@"stringArray: %@",stringArray);

    //字符串数组 转为 字符串数组长度的数组
    NSArray<NSNumber*> *lengthArr = [stringArray valueForKeyPath:@"length"];
    NSLog(@"lengthArray: %@",lengthArr);

//控制台输出如下: 
stringArray: (
              2,
              3,
              99,
              6,
              10
              )

lengthArray: (
              1,
              1,
              2,
              1,
              2
              )

数组每个子元素调用指定方法

    NSArray<NSString *> *nameArr = @[@"CoderWGB",@"Apple",@"iOS",@"Android",@"Flutter"];
    //调用系统方法
    NSLog(@"全部转小写: %@",[nameArr valueForKeyPath:@"lowercaseString"]);
    NSLog(@"全部转大写: %@",[nameArr valueForKeyPath:@"uppercaseString"]);
    NSLog(@"全部首字符大写: %@",[nameArr valueForKeyPath:@"capitalizedString"]);
    // 调用自定义方法
    NSLog(@"全部元素之前插入  字符: %@",[nameArr valueForKeyPath:@"formatApplePrefix"]);

//写一个自定义方法
@interface NSString (Extension)
- (NSString *)formatApplePrefix;
@end

@implementation  NSString (Extension)
- (NSString *)formatApplePrefix{
    return [NSString stringWithFormat:@"  %@",self];
}
@end

//控制台打印如下: 
全部转小写: (
    coderwgb,
    apple,
    ios,
    android,
    flutter
)
 全部转大写: (
    CODERWGB,
    APPLE,
    IOS,
    ANDROID,
    FLUTTER
)
全部首字符大写: (
    Coderwgb,
    Apple,
    Ios,
    Android,
    Flutter
)
全部元素之前插入  字符: (
    " \Uf8ff CoderWGB",
    " \Uf8ff Apple",
    " \Uf8ff iOS",
    " \Uf8ff Android",
    " \Uf8ff Flutter"
)

比起自己写循环遍历去拼接字符串什么的,效果还是挺明显的,并且调用代码相对解耦,可以把业务逻辑分离出去