ExistOrLive's Blog

Objective-c KVC

 
  • Jun 08, 2020

KVC(Key-Value Coding)，允许开发者通过key或者keyPath直接访问对象的属性，或者为对象的属性赋值而不用调用明确的存取方法


// NSObject的NSKeyValueCoding分类提供了KVC的相关方法

@interface NSObject(NSKeyValueCoding)

- (nullable id)valueForKey:(NSString *)key;
- (void)setValue:(nullable id)value forKey:(NSString *)key;

- (nullable id)valueForKeyPath:(NSString *)keyPath;
- (void)setValue:(nullable id)value forKeyPath:(NSString *)keyPath;


- (BOOL)validateValue:(inout id _Nullable * _Nonnull)ioValue forKey:(NSString *)inKey error:(out NSError **)outError;

- (nullable id)valueForUndefinedKey:(NSString *)key;
- (void)setValue:(nullable id)value forUndefinedKey:(NSString *)key;
- (void)setNilValueForKey:(NSString *)key;

... 

@end

KVC的使用

@interface

KVC的过程

-valueForKey:

  1. 查询对象是否有符合-get<Key>,-<key>或者-is<Key>的方法，如果有，则直接调用并返回；否则进入下一步。