iOS KVC详解

1
2
3
4
5
- (nullable id)valueForKey:(NSString *)key;                          //直接通过Key来取值
- (void)setValue:(nullable id)value forKey:(NSString *)key;          //通过Key来设值
- (nullable id)valueForKeyPath:(NSString *)keyPath;                  //通过KeyPath来取值
- (void)setValue:(nullable id)value forKeyPath:(NSString *)keyPath;  //通过KeyPath来设值

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
+ (BOOL)accessInstanceVariablesDirectly;
//默认返回YES，表示如果没有找到Set<Key>方法的话，会按照_key，_iskey，key，iskey的顺序搜索成员，设置成NO就不这样搜索
- (BOOL)validateValue:(inout id __nullable * __nonnull)ioValue forKey:(NSString *)inKey error:(out NSError **)outError;
//KVC提供属性值正确性�验证的API，它可以用来检查set的值是否正确、为不正确的值做一个替换值或者拒绝设置新值并返回错误原因。
- (NSMutableArray *)mutableArrayValueForKey:(NSString *)key;
//这是集合操作的API，里面还有一系列这样的API，如果属性是一个NSMutableArray，那么可以用这个方法来返回。
- (nullable id)valueForUndefinedKey:(NSString *)key;
//如果Key不存在，且没有KVC无法搜索到任何和Key有关的字段或者属性，则会调用这个方法，默认是抛出异常。
- (void)setValue:(nullable id)value forUndefinedKey:(NSString *)key;
//和上一个方法一样，但这个方法是设值。
- (void)setNilValueForKey:(NSString *)key;
//如果你在SetValue方法时面给Value传nil，则会调用这个方法
- (NSDictionary<NSString *, id> *)dictionaryWithValuesForKeys:(NSArray<NSString *> *)keys;
//输入一组key,返回该组key对应的Value，再转成字典返回，用于将Model转到字典。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
#import <Foundation/Foundation.h>
@interface Test: NSObject {
    NSString *_name;
}
@end
@implementation Test
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC赋值name
        [obj setValue:@"xiaoming" forKey:@"name"];
        //通过KVC取值name打印
        NSLog(@"obj的名字是%@", [obj valueForKey:@"name"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
#import <Foundation/Foundation.h>
@interface Test: NSObject {
    NSString *_name;
}
@end
@implementation Test
+ (BOOL)accessInstanceVariablesDirectly {
    return NO;
}
- (id)valueForUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@",key);
    return nil;
}
- (void)setValue:(id)value forUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@", key);
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC赋值name
        [obj setValue:@"xiaoming" forKey:@"name"];
        //通过KVC取值name打印
        NSLog(@"obj的名字是%@", [obj valueForKey:@"name"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
#import <Foundation/Foundation.h>
@interface Test: NSObject {
    NSString *_isName;
}
@end
@implementation Test
+ (BOOL)accessInstanceVariablesDirectly {
    return YES;
}
- (id)valueForUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@",key);
    return nil;
}
- (void)setValue:(id)value forUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@", key);
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC赋值name
        [obj setValue:@"xiaoming" forKey:@"name"];
        //通过KVC取值name打印
        NSLog(@"obj的名字是%@", [obj valueForKey:@"name"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
#import <Foundation/Foundation.h>
@interface Test: NSObject {
}
@end
@implementation Test
- (NSUInteger)getAge {
    return 10;
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC取值age打印
        NSLog(@"obj的年龄是%@", [obj valueForKey:@"age"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
#import <Foundation/Foundation.h>
@interface Test: NSObject {
}
@end
@implementation Test
- (NSUInteger)age {
    return 10;
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC取值age打印
        NSLog(@"obj的年龄是%@", [obj valueForKey:@"age"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
#import <Foundation/Foundation.h>
@interface Test: NSObject {
}
@end
@implementation Test
- (NSUInteger)isAge {
    return 10;
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //生成对象
        Test *obj = [[Test alloc] init];
        //通过KVC取值age打印
        NSLog(@"obj的年龄是%@", [obj valueForKey:@"age"]);
        
    }
    return 0;
}

1
2
3
- (nullable id)valueForKeyPath:(NSString *)keyPath;                  //通过KeyPath来取值
- (void)setValue:(nullable id)value forKeyPath:(NSString *)keyPath;  //通过KeyPath来设值

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
#import <Foundation/Foundation.h>
@interface Test1: NSObject {
    NSString *_name;
}
@end
@implementation Test1
@end
@interface Test: NSObject {
    Test1 *_test1;
}
@end
@implementation Test
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //Test生成对象
        Test *test = [[Test alloc] init];
        //Test1生成对象
        Test1 *test1 = [[Test1 alloc] init];
        //通过KVC设值test的"test1"
        [test setValue:test1 forKey:@"test1"];
        //通过KVC设值test的"test1的name"
        [test setValue:@"xiaoming" forKeyPath:@"test1.name"];
        //通过KVC取值age打印
        NSLog(@"test的"test1的name"是%@", [test valueForKeyPath:@"test1.name"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
#import <Foundation/Foundation.h>
@interface Test: NSObject {
    NSUInteger age;
}
@end
@implementation Test
- (void)setNilValueForKey:(NSString *)key {
    NSLog(@"不能将%@设成nil", key);
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //Test生成对象
        Test *test = [[Test alloc] init];
        //通过KVC设值test的age
        [test setValue:nil forKey:@"age"];
        //通过KVC取值age打印
        NSLog(@"test的年龄是%@", [test valueForKey:@"age"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
#import <Foundation/Foundation.h>
@interface Test: NSObject {
}
@end
@implementation Test
- (id)valueForUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@",key);
    return nil;
}
- (void)setValue:(id)value forUndefinedKey:(NSString *)key {
    NSLog(@"出现异常，该key不存在%@", key);
}
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        
        //Test生成对象
        Test *test = [[Test alloc] init];
        //通过KVC设值test的age
        [test setValue:@10 forKey:@"age"];
        //通过KVC取值age打印
        NSLog(@"test的年龄是%@", [test valueForKey:@"age"]);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
//  Person.m
#import "Person.h"
 
@interface Person ()
 
@property (nonatomic,assign) NSInteger age;
 
@end
 
 
@implementation Person
 
@end

1
2
[person setValue:[NSNumber numberWithInteger:5] forKey:@"age"];

1
2
[person valueForKey:@"age"];

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
//  ViewController.m
#import "ViewController.h"
#import "Person.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    Person *person = [[Person alloc]init];
    [person setValue:[NSNumber numberWithInteger:5] forKey:@"age"];
    NSLog(@"age=%@",[person valueForKey:@"age"]);
    
}
@end

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
#import <Foundation/Foundation.h>
@interface Book : NSObject
@property (nonatomic, copy)  NSString* name;
@property (nonatomic, assign)  CGFloat price;
@end
@implementation Book
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        Book *book1 = [Book new];
        book1.name = @"The Great Gastby";
        book1.price = 10;
        Book *book2 = [Book new];
        book2.name = @"Time History";
        book2.price = 20;
        Book *book3 = [Book new];
        book3.name = @"Wrong Hole";
        book3.price = 30;
        
        Book *book4 = [Book new];
        book4.name = @"Wrong Hole";
        book4.price = 40;
        
        NSArray* arrBooks = @[book1,book2,book3,book4];
        NSNumber* sum = [arrBooks valueForKeyPath:@"@sum.price"];
        NSLog(@"sum:%f",sum.floatValue);
        NSNumber* avg = [arrBooks valueForKeyPath:@"@avg.price"];
        NSLog(@"avg:%f",avg.floatValue);
        NSNumber* count = [arrBooks valueForKeyPath:@"@count"];
        NSLog(@"count:%f",count.floatValue);
        NSNumber* min = [arrBooks valueForKeyPath:@"@min.price"];
        NSLog(@"min:%f",min.floatValue);
        NSNumber* max = [arrBooks valueForKeyPath:@"@max.price"];
        NSLog(@"max:%f",max.floatValue);
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
#import <Foundation/Foundation.h>
@interface Book : NSObject
@property (nonatomic, copy)  NSString* name;
@property (nonatomic, assign)  CGFloat price;
@end
@implementation Book
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        Book *book1 = [Book new];
        book1.name = @"The Great Gastby";
        book1.price = 40;
        Book *book2 = [Book new];
        book2.name = @"Time History";
        book2.price = 20;
        Book *book3 = [Book new];
        book3.name = @"Wrong Hole";
        book3.price = 30;
        
        Book *book4 = [Book new];
        book4.name = @"Wrong Hole";
        book4.price = 10;
        
        NSArray* arrBooks = @[book1,book2,book3,book4];
        
        NSLog(@"distinctUnionOfObjects");
        NSArray* arrDistinct = [arrBooks valueForKeyPath:@"@distinctUnionOfObjects.price"];
        for (NSNumber *price in arrDistinct) {
            NSLog(@"%f",price.floatValue);
        }
        NSLog(@"unionOfObjects");
        NSArray* arrUnion = [arrBooks valueForKeyPath:@"@unionOfObjects.price"];
        for (NSNumber *price in arrUnion) {
            NSLog(@"%f",price.floatValue);
        }
        
    }
    return 0;
}

1
2
3
- (NSDictionary<NSString *, id> *)dictionaryWithValuesForKeys:(NSArray<NSString *> *)keys;
- (void)setValuesForKeysWithDictionary:(NSDictionary<NSString *, id> *)keyedValues;

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
#import <Foundation/Foundation.h>
@interface Address : NSObject
@end
@interface Address()
@property (nonatomic, copy)NSString* country;
@property (nonatomic, copy)NSString* province;
@property (nonatomic, copy)NSString* city;
@property (nonatomic, copy)NSString* district;
@end
@implementation Address
@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        //模型转字典
        Address* add = [Address new];
        add.country = @"China";
        add.province = @"Guang Dong";
        add.city = @"Shen Zhen";
        add.district = @"Nan Shan";
        NSArray* arr = @[@"country",@"province",@"city",@"district"];
        NSDictionary* dict = [add dictionaryWithValuesForKeys:arr]; //把对应key所有的属性全部取出来
        NSLog(@"%@",dict);
        
        //字典转模型
        NSDictionary* modifyDict = @{@"country":@"USA",@"province":@"california",@"city":@"Los angle"};
        [add setValuesForKeysWithDictionary:modifyDict];            //用key Value来修改Model的属性
        NSLog(@"country:%@  province:%@ city:%@",add.country,add.province,add.city);
        
        
    }
    return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        NSArray* arrStr = @[@"english",@"franch",@"chinese"];
        NSArray* arrCapStr = [arrStr valueForKey:@"capitalizedString"];
        for (NSString* str  in arrCapStr) {
            NSLog(@"%@",str);
        }
        NSArray* arrCapStrLength = [arrStr valueForKeyPath:@"capitalizedString.length"];
        for (NSNumber* length  in arrCapStrLength) {
            NSLog(@"%ld",(long)length.integerValue);
        }
        
    }
    return 0;
}