一、KVC简单介绍
KVC key valued coding 键值编码
KVC通过键值间接编码
补充：
与KVC相对的时KVO，即key valued observer 键值观察。监听某一个模型的属性，只要模型属性的值一变化就通知你。
二、代码颜色
1> 通过KVC设置值 setValue: forKey：
1，1>
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
[p1 setValue:@"zhangsan" forKey:@"name"];
p1.age = 18;
NSLog(@"name = %@, age = %d", p1.name, p1.age);
}
return 0;
}
通过执行结果可以看到这个方法通过对象的属性值设置value。
1,2> 通过KVC设置值 setValue: forKeyPath：
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
[p1 setValue:@"zhangsan" forKeyPath:@"name"];
p1.age = 18;
NSLog(@"name = %@, age = %d", p1.name, p1.age);
}
return 0;
}
可以看到两个方法执行效果一样，
[setValue:@"zhangsan" forKeyPath:@"name"];
要看到这个方法的好处，可以看下面这个例子：
1.3>
#import <Foundation/Foundation.h>
@interface Book : NSObject
@property (nonatomic, copy) NSString *bookName;
@end
@implementation Book
@end
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
Book *b1 = [[Book alloc] init];
p1.book = b1;
[p1 setValue:@"同桌的你" forKeyPath:@"book.bookName"];
NSLog(@"bookName = %@", b1.bookName);
}
return 0;
}
用KVC取一个嵌套层次很深的路径的时候，只要诶它一个路径就能把想要的属性给拿出来。（.可以理解为路径。一直一直进入）。能够帮助我们很方便的编码。
2,通过KVC取值：
#import <Foundation/Foundation.h>
@interface Book : NSObject
@property (nonatomic, copy) NSString *bookName;
@end
@implementation Book
@end
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
Book *b1 = [[Book alloc] init];
b1.bookName = @"同桌的你";
p1.book = b1;
NSString *bookName = [p1 valueForKeyPath:@"book.bookName"];
NSLog(@"bookName = %@", bookName);
}
return 0;
}
结果：
当然我们也可以通过valueForKey:取值不过只能取person对象的属性的值，不能取到book对象中的属性值
3，将person对象放入到数组中，通过数组取的person对象中属性的值
代码：
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
p1.name = @"zhangsan";
Person *p2 = [[Person alloc] init];
p2.name = @"lisi";
NSArray *array = @[p1, p2];
NSArray *name = [array valueForKeyPath:@"name"];
NSLog(@"%@", name);
}
return 0;
}
结论：将对象放入到数组中，可以通过数组的valueForKeyPath：方法取出数组中存放对象的属性值，返回一个存放属性值的数组对象
4>KVC在字典中的应用
4.1 可以将字典中的键对应的值赋给对象的属性值
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
NSDictionary *dic = @{@"name":@"zhangsan"};
[p1 setValuesForKeysWithDictionary:dic];
NSLog(@"%@", p1.name);
}
return 0;
}
4.2 可以将对象的属性值赋给字典键对应的值
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) Book *book;
@end
@implementation Person
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
Person *p1 = [[Person alloc] init];
p1.name = @"zhangsan";
p1.age = 19;
NSDictionary *dic = [p1 dictionaryWithValuesForKeys:@[@"name", @"age"]];
NSLog(@"%@", dic);
}
return 0;
}
用KVC取一个嵌套层次很深的路径的时候，只要诶它一个路径就能把想要的属性给拿出来。（.可以理解为路径。一直一直进入）。能够帮助我们很方便的编码
时间： 2024-10-10 23:38:43