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  • iOS 运行时添加属性和方法

    第一种:runtime.h里的方法
    BOOL class_addProperty(Class cls,
        const char *name,
        const objc_property_attribute_t *attributes,
        unsigned int attributeCount)
    #include <objc/runtime.h>
    #import <Foundation/Foundation.h>
    
    @interface SomeClass : NSObject {
        NSString *_privateName;
    }
    @end
    
    @implementation SomeClass
    - (id)init {
        self = [super init];
        if (self) _privateName = @"Steve";
        return self;
    }
    @end
    NSString *nameGetter(id self, SEL _cmd) {
        Ivar ivar = class_getInstanceVariable([SomeClass class], "_privateName");
        return object_getIvar(self, ivar);
    }
    
    void nameSetter(id self, SEL _cmd, NSString *newName) {
        Ivar ivar = class_getInstanceVariable([SomeClass class], "_privateName");
        id oldName = object_getIvar(self, ivar);
        if (oldName != newName) object_setIvar(self, ivar, [newName copy]);
    }
    
    int main(void) {
        @autoreleasepool {
            objc_property_attribute_t type = { "T", "@"NSString"" };
            objc_property_attribute_t ownership = { "C", "" }; // C = copy
            objc_property_attribute_t backingivar  = { "V", "_privateName" };
            objc_property_attribute_t attrs[] = { type, ownership, backingivar };
            class_addProperty([SomeClass class], "name", attrs, 3);
            class_addMethod([SomeClass class], @selector(name), (IMP)nameGetter, "@@:");
            class_addMethod([SomeClass class], @selector(setName:), (IMP)nameSetter, "v@:@");
    
            id o = [SomeClass new];
            NSLog(@"%@", [o name]);
            [o setName:@"Jobs"];
            NSLog(@"%@", [o name]);
        }
    }
    输出:
    Steve
    Jobs
    第二种:
    - (id)valueForUndefinedKey:(NSString *)key
    第三种:
    static char const * const ObjectTagKey;
    
    @implementation NSObject (ExampleCategoryWithProperty)
    @dynamic objectTag;
    
    - (id)objectTag {
        return objc_getAssociatedObject(self, ObjectTagKey);
    }
    
    - (void)setObjectTag:(id)newObjectTag {
        objc_setAssociatedObject(self, ObjectTagKey, newObject, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }

    
    

    版权声明:本文为博主原创文章,未经博主允许不得转载。

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  • 原文地址:https://www.cnblogs.com/zsw-1993/p/4879560.html
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