iOS load和initialize方法
一个类的load方法，当类加载到OC运行时环境(内存)中,就会调用一次(一个类只会加载1次)
(void)load { _instance = [[self alloc] init]; NSLog(@'load'); }一个类的initialize方法，当第一次使用这个类的时候才会调用
(void)initialize
{
NSLog(@'initialize');
}
load方法和initialize方法的区别
新建一个类DYPerson和它的子类DYStudent。
#import <Foundation/Foundation.h> @interface DYPerson : NSObject @end #import 'DYPerson.h' @implementation DYPerson (void)load { NSLog(@'DYPerson-->load'); } (void)initialize { NSLog(@'DYPerson-->initialize'); } @end #import 'DYPerson.h' @interface DYStudent : DYPerson @end #import 'DYStudent.h' @implementation DYStudent (void)load { NSLog(@'DYStudent-->load'); } (void)initialize { NSLog(@'DYStudent-->initialize'); } @end 在ViewController里面调用DYPerson *person = [[DYPerson alloc] init];则会打印 2017-05-04 00:38:36.422 AnimationArray[6544:2798211] DYPerson-->load 2017-05-04 00:38:36.426 AnimationArray[6544:2798211] DYStudent-->load 2017-05-04 00:38:36.810 AnimationArray[6544:2798211] DYPerson-->initialize若在ViewController里面调用DYStudent *student = [DYStudent alloc] init];则会打印
2017-05-04 00:47:28.540 AnimationArray[7029:2804754] DYPerson-->load
2017-05-04 00:47:28.543 AnimationArray[7029:2804754] DYStudent-->load
2017-05-04 00:47:28.682 AnimationArray[7029:2804754] DYPerson-->initialize
2017-05-04 00:47:28.682 AnimationArray[7029:2804754] DYStudent-->initialize
因为DYStudent是DYPerson的子类,在调用init方法的时候会调用父类(DYPerson)的init方法,进而使用DYPerson从而打印DYPerson-->initialize。
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