定义LGPerson和LGStudent类

typedef struct {
    float x, y, z;
} ThreeFloats;

@interface LGPerson : NSObject{
   @public
   NSString *myName;
}

@property (nonatomic, copy)   NSString          *name;
@property (nonatomic, strong) NSArray           *array;
@property (nonatomic, strong) NSMutableArray    *mArray;
@property (nonatomic, assign) int age;
@property (nonatomic)         ThreeFloats       threeFloats;
@property (nonatomic, strong) LGStudent         *student;

@end

@interface LGStudent : NSObject
@property (nonatomic, copy)   NSString          *name;
@property (nonatomic, copy)   NSString          *subject;
@property (nonatomic, copy)   NSString          *nick;
@property (nonatomic, assign) int               age;
@property (nonatomic, assign) int               length;
@property (nonatomic, strong) NSMutableArray    *penArr;
@end

一、KVC 的防问

调用一般的setter方法

LGPerson *person = [[LGPerson alloc] init];
person.name      = @"LG_Cooci"; // setter -- llvm
person.age       = 18;
person->myName   = @"cooci";
NSLog(@"%@ - %d - %@",person.name,person.age,person->myName);

打印结果：

都赋值成功了

调用setValue:forkey:方法

[person setValue:@"KC" forKey:@"name"];

同样可以设置成功

集合类的赋值

NSArray *array = [person valueForKey:@"array"];
array = @[@"100",@"2",@"3"];
[person setValue:array forKey:@"array"];
NSLog(@"%@",[person valueForKey:@"array"]);

给不可变数组赋值

NSMutableArray *mArray = [person mutableArrayValueForKey:@"array"];
[person mutableArrayValueForKey:@"array"];
mArray[0] = @"200";
NSLog(@"%@",[person valueForKey:@"array"]);

结结构体属性赋值

ThreeFloats floats = {1.,2.,3.};
    NSValue *value     = [NSValue valueWithBytes:&floats objCType:@encode(ThreeFloats)];
[person setValue:value forKey:@"threeFloats"];
NSValue *value1    = [person valueForKey:@"threeFloats"];
NSLog(@"%@",value1);   
ThreeFloats th;
[value1 getValue:&th];
NSLog(@"%f-%f-%f",th.x,th.y,th.z);

使用setValue:forKeyPath:给模型属性的属性赋值

LGStudent *student = [LGStudent alloc];
student.subject    = @"大师班";
person.student     = student;
[person setValue:@"Swift" forKeyPath:@"student.subject"];
NSLog(@"%@",[person valueForKeyPath:@"student.subject"]);

数组的取值

- (void)arrayDemo{
    LGStudent *p = [LGStudent new];
    p.penArr = [NSMutableArray arrayWithObjects:@"pen0", @"pen1", @"pen2", @"pen3", nil];
    NSArray *arr = [p valueForKey:@"penArr"]; // 动态成员变量
    NSLog(@"pens = %@", arr);
    //NSLog(@"%@",arr[0]);
    NSLog(@"%d",[arr containsObject:@"pen9"]);
    // 遍历
    NSEnumerator *enumerator = [arr objectEnumerator];
    NSString* str = nil;
    while (str = [enumerator nextObject]) {
        NSLog(@"%@", str);
    }
}

字典与模型的相互转换

- (void)dictionaryTest{
    
    NSDictionary* dict = @{
                           @"name":@"Cooci",
                           @"nick":@"KC",
                           @"subject":@"iOS",
                           @"age":@18,
                           @"length":@180
                           };
    LGStudent *p = [[LGStudent alloc] init];
    // 字典转模型
    [p setValuesForKeysWithDictionary:dict];
    NSLog(@"%@",p);
    // 键数组转模型到字典
    NSArray *array = @[@"name",@"age",@"nick",@"subject",@"length"];
    NSDictionary *dic = [p dictionaryWithValuesForKeys:array];
    NSLog(@"%@",dic);
}

setValuesForKeysWithDictionary:将字典转为对应的模型； dictionaryWithValuesForKeys:将模型转为字典.

KVC消息传递

- (void)arrayMessagePass{
    NSArray *array = @[@"Hank",@"Cooci",@"Kody",@"CC"];
    NSArray *lenStr= [array valueForKeyPath:@"length"];
    NSLog(@"%@",lenStr);// 消息从array传递给了string
    NSArray *lowStr= [array valueForKeyPath:@"lowercaseString"];
    NSLog(@"%@",lowStr);
}

• [array valueForKeyPath:@"length"]获取数组中字符串数据的长度；

• [array valueForKeyPath:@"lowercaseString"]让数组中的字符串成员首字母小写.

这两个方法都实现了将消息从NSArray传递到他的NSString元素.

聚合操作符

- (void)aggregationOperator{
    NSMutableArray *personArray = [NSMutableArray array];
    for (int i = 0; i < 6; i++) {
        LGStudent *p = [LGStudent new];
        NSDictionary* dict = @{
                               @"name":@"Tom",
                               @"age":@(18+i),
                               @"nick":@"Cat",
                               @"length":@(175 + 2*arc4random_uniform(6)),
                               };
        [p setValuesForKeysWithDictionary:dict];
        [personArray addObject:p];
    }
    NSLog(@"%@", [personArray valueForKey:@"length"]);
    
    /// 平均身高
    float avg = [[personArray valueForKeyPath:@"@avg.length"] floatValue];
    NSLog(@"%f", avg);
    
    int count = [[personArray valueForKeyPath:@"@count.length"] intValue];
    NSLog(@"%d", count);
    
    int sum = [[personArray valueForKeyPath:@"@sum.length"] intValue];
    NSLog(@"%d", sum);
    
    int max = [[personArray valueForKeyPath:@"@max.length"] intValue];
    NSLog(@"%d", max);
    
    int min = [[personArray valueForKeyPath:@"@min.age"] intValue];
    NSLog(@"%d", min);
}

• personArray中的元素是LGStudent对象；
• [personArray valueForKey:@"length"]获取数组元素中的所有属性length的值；
• [personArray valueForKeyPath:@"@count.length"]获取属性length的个数、平均值、最大值、最小值和和。

数组操作符

- (void)arrayOperator{
    NSMutableArray *personArray = [NSMutableArray array];
    for (int i = 0; i < 6; i++) {
        LGStudent *p = [LGStudent new];
        NSDictionary* dict = @{
                               @"name":@"Tom",
                               @"age":@(18+i),
                               @"nick":@"Cat",
                               @"length":@(175 + 2*arc4random_uniform(6)),
                               };
        [p setValuesForKeysWithDictionary:dict];
        [personArray addObject:p];
    }
    NSLog(@"%@", [personArray valueForKey:@"length"]);
    // 返回操作对象指定属性的集合
    NSArray* arr1 = [personArray valueForKeyPath:@"@unionOfObjects.length"];
    NSLog(@"arr1 = %@", arr1);
    // 返回操作对象指定属性的集合 -- 去重
    NSArray* arr2 = [personArray valueForKeyPath:@"@distinctUnionOfObjects.length"];
    NSLog(@"arr2 = %@", arr2);
    
}

• [personArray valueForKeyPath:@"@unionOfObjects.length"]返回操作对象指定属性的集合;
• [personArray valueForKeyPath:@"@distinctUnionOfObjects.length"]返回操作对旬指定属性的集合，会去重。

数组操作数组中元素某属性的操作符

- (void)arrayNesting{
    
    NSMutableArray *personArray1 = [NSMutableArray array];
    for (int i = 0; i < 6; i++) {
        LGStudent *student = [LGStudent new];
        NSDictionary* dict = @{
                               @"name":@"Tom",
                               @"age":@(18+i),
                               @"nick":@"Cat",
                               @"length":@(175 + 2*arc4random_uniform(6)),
                               };
        [student setValuesForKeysWithDictionary:dict];
        [personArray1 addObject:student];
    }
    
    NSMutableArray *personArray2 = [NSMutableArray array];
    for (int i = 0; i < 6; i++) {
        LGStudent *person = [LGStudent new];
        NSDictionary* dict = @{
                               @"name":@"Tom",
                               @"age":@(18+i),
                               @"nick":@"Cat",
                               @"length":@(175 + 2*arc4random_uniform(6)),
                               };
        [person setValuesForKeysWithDictionary:dict];
        [personArray2 addObject:person];
    }
    
    // 嵌套数组
    NSArray* nestArr = @[personArray1, personArray2];
    
    NSArray* arr = [nestArr valueForKeyPath:@"@distinctUnionOfArrays.length"];
    NSLog(@"arr = %@", arr);
    
    NSArray* arr1 = [nestArr valueForKeyPath:@"@unionOfArrays.length"];
    NSLog(@"arr1 = %@", arr1);

依旧可以取出nestArr中两个元素personArray1和personArray2数组的元素的属性 length的数组。

KVC的设值取值分析

设值分析

设值方法的调用顺序

[person setValue:@"LG_Cooci" forKey:@"name"]设值流程按如下顺序依次调用

先看setName:有没有实现，再看_setName:有没有实现，再看setIsName:有没有实现，最后看_setIsName:有没有实现。

如果以上方法都没有实现，回查看：

+ (BOOL)accessInstanceVariablesDirectly{
    return YES;
}

是否返回为NO,为NO则调用：

-(void)setValue:(id)value forUndefinedKey:(NSString *)key{
    
}

否则查找如下成员变量

直接通过成员变量查找的赋值流程

person->_name = @"_name";
person->_isName = @"_isName";
person->name = @"name";
person->isName = @"isName";
NSLog(@"取值:%@",[person valueForKey:@"name"]);

取值流程

- (NSString *)getName{
    return NSStringFromSelector(_cmd);
}

- (NSString *)name{
    return NSStringFromSelector(_cmd);
}

- (NSString *)isName{
    return NSStringFromSelector(_cmd);
}

- (NSString *)_name{
    return NSStringFromSelector(_cmd);
}

[person valueForKey:@"name"]查找成员变量的调用以上方法的顺序：

先调用getName,再调用name,再调用isName,最后调用_name。

总结