IOS KVC搜尋順序

2014-07-11 Kommentare IOS

直接上CODE

Dream.m
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@interface Dream()
{
    NSString *_dream;
    NSString *dream;
}
@end

@implementation Dream

-(instancetype)init{
    self = [super init];
    if (self) {
        _dream = @"Yume4";
        dream = @"Yume5";
    }
    return self;
}

-(NSString *)getDream{
    return @"Yume1H";
}

-(NSString *)dream{
    return @"Yume2H";
}

-(NSString *)isDream{
    return @"Yume3H";
}

-(NSString *)_getDream{
    return @"Yume1M";
}

-(NSString *)_dream{
    return @"Yume2M";
}

-(NSString *)_isDream{
    return @"Yume3M";
}

-(id)valueForUndefinedKey:(NSString *)key{
    if ([key isEqualTo:@"dream"]) {
        return @"Yume6";
    }
    return nil;
}

@end

Test Code
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Dream *dream = [Dream new];
NSLog(@"%@",[dream valueForKey:@"dream"]);

在這篇簡報Intro to Cocoa KVC/KVO and Bindings(Page 13)上有提到KVC依序搜尋執行的順序

  1. Search for a public accessor (‘getLastName’ or ‘lastName’)
  2. If not found, search for a private accessor method based on key (‘_getLastName’ or ‘_lastName’).
  3. If not found’ search for an instance variable (_lastName or lastName)
  4. If not found, invoke valueForUndefinedKey:

實測

  1. 首先先找方法 getDream -> dream -> isDream
  2. 再找方法 _getDream -> _dream -> _isDream
  3. 再找 instance variable _dream -> dream
  4. 最後呼叫valueForUndefinedKey:
#IOS #KVC