OC-类的加载和初始化
from : http://www.cnblogs.com/wendingding/p/3709569.html
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// // Person.h // WDDClassTest // // Created by LiuChanghong on 15/9/25. // Copyright © 2015年 LiuChanghong. All rights reserved. // #import <Foundation/Foundation.h> @interface Person : NSObject @end
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// // Person.m // WDDClassTest // // Created by LiuChanghong on 15/9/25. // Copyright © 2015年 LiuChanghong. All rights reserved. // #import "Person.h" @implementation Person //重写+load和+initialize方法 +(void)load{ NSLog(@"Person +load"); } +(void)initialize{ NSLog(@"Person +initialize"); } @end
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// // Student.h // WDDClassTest // // Created by LiuChanghong on 15/9/25. // Copyright © 2015年 LiuChanghong. All rights reserved. // #import "Person.h" @interface Student : Person @end
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// // Student.m // WDDClassTest // // Created by LiuChanghong on 15/9/25. // Copyright © 2015年 LiuChanghong. All rights reserved. // #import "Student.h" @implementation Student //重写+load和+initialize方法 +(void)load{ NSLog(@"Student +load"); } +(void)initialize{ NSLog(@"Student +initialize"); } @end
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// // main.m // WDDClassTest // // Created by LiuChanghong on 15/9/25. // Copyright © 2015年 LiuChanghong. All rights reserved. // #import <Foundation/Foundation.h> #import "Student.h" int main(int argc, const char * argv[]) { @autoreleasepool { /* 1.当程序启动时,就会加载项目中所有的类和分类,而且加载后会调用每个类和分类的+load方法,只会调用一次; 2.当第一次使用某个类时,就会调用当前类的+initialize方法,仅第一次; 3.先加载父类,再加载子类(先调用父类的+load方法,再调用子类的+load方法,最后调用分类的+load方法),先初始化父类,再初始化子类(先调用父类的+initialize方法,再调用子类的+initialize方法)。 4.注意:在初始化的时候,如果在分类中重写了+initialize方法,则会覆盖掉父类的。 5.重写+initialize方法可以监听类的使用情况。 */ Person *person1 = [Person new]; Person *person2 = [Person new]; Person *person3 = [Person new]; Student *student1 = [Student new]; Student *student2 = [Student new]; Student *student3 = [Student new]; } return 0; }
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