ios動態添加屬性的幾種方法

http://blog.csdn.net/shengyumojian/article/details/44919695

在ios運行過程中，有幾種方式能夠動態的添加屬性。

 

1-通過runtime動態關聯對象

 

主要用到了objc_setAssociatedObject，objc_getAssociatedObject以及objc_removeAssociatedObjects

 

//在目標target上添加關聯對象，屬性名propertyname(也能用來添加block)，值value
+ (void)addAssociatedWithtarget:(id)target withPropertyName:(NSString *)propertyName withValue:(id)value {
    id property = objc_getAssociatedObject(target, &propertyName);

    if(property == nil)
    {
        property = value;
        objc_setAssociatedObject(target, &propertyName, property, OBJC_ASSOCIATION_RETAIN);
    }
}

//獲取目標target的指定關聯對象值
+ (id)getAssociatedValueWithTarget:(id)target withPropertyName:(NSString *)propertyName {
    id property = objc_getAssociatedObject(target, &propertyName);
    return property;
}

優點：這種方式能夠使我們快速的在一個已有的class內部添加一個動態屬性或block塊。

 

缺點：不能像遍歷屬性一樣的遍歷我們所有關聯對象，且不能移除制定的關聯對象，只能通過removeAssociatedObjects方法移除所有關聯對象。

 

2-通過runtime動態添加Ivar

 

主要用到objc_allocateClassPair，class_addIvar，objc_registerClassPair

 

//在目標target上添加屬性(已經存在的類不支持，可跳進去看注釋)，屬性名propertyname，值value
+ (void)addIvarWithtarget:(id)target withPropertyName:(NSString *)propertyName withValue:(id)value {
    if (class_addIvar([target class], [propertyName UTF8String], sizeof(id), log2(sizeof(id)), "@")) {
        YYLog(@"創建屬性Ivar成功");
    }
}

//獲取目標target的指定屬性值
+ (id)getIvarValueWithTarget:(id)target withPropertyName:(NSString *)propertyName {
    Ivar ivar = class_getInstanceVariable([target class], [propertyName UTF8String]);
    if (ivar) {
        id value = object_getIvar(target, ivar);
        return value;
    } else {
        return nil;
    }
}

優點：動態添加Ivar我們能夠通過遍歷Ivar得到我們所添加的屬性。

 

缺點：不能在已存在的class中添加Ivar，所有說必須通過objc_allocateClassPair動態創建一個class，才能調用class_addIvar創建Ivar，最后通過objc_registerClassPair注冊class。

 

3-通過runtime動態添加property

 

主要用到class_addProperty，class_addMethod，class_replaceProperty，class_getInstanceVariable

 

//在目標target上添加屬性，屬性名propertyname，值value
+ (void)addPropertyWithtarget:(id)target withPropertyName:(NSString *)propertyName withValue:(id)value {

    //先判斷有沒有這個屬性，沒有就添加，有就直接賦值
    Ivar ivar = class_getInstanceVariable([target class], [[NSString stringWithFormat:@"_%@", propertyName] UTF8String]);
    if (ivar) {
        return;
    }

    /*
     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);
     */

    //objc_property_attribute_t所代表的意思可以調用getPropertyNameList打印，大概就能猜出
    objc_property_attribute_t type = { "T", [[NSString stringWithFormat:@"@\"%@\"",NSStringFromClass([value class])] UTF8String] };
    objc_property_attribute_t ownership = { "&", "N" };
    objc_property_attribute_t backingivar  = { "V", [[NSString stringWithFormat:@"_%@", propertyName] UTF8String] };
    objc_property_attribute_t attrs[] = { type, ownership, backingivar };
    if (class_addProperty([target class], [propertyName UTF8String], attrs, 3)) {

        //添加get和set方法
        class_addMethod([target class], NSSelectorFromString(propertyName), (IMP)getter, "@@:");
        class_addMethod([target class], NSSelectorFromString([NSString stringWithFormat:@"set%@:",[propertyName capitalizedString]]), (IMP)setter, "v@:@");

        //賦值
        [target setValue:value forKey:propertyName];
        NSLog(@"%@", [target valueForKey:propertyName]);

        YYLog(@"創建屬性Property成功");
    } else {
        class_replaceProperty([target class], [propertyName UTF8String], attrs, 3);
        //添加get和set方法
        class_addMethod([target class], NSSelectorFromString(propertyName), (IMP)getter, "@@:");
        class_addMethod([target class], NSSelectorFromString([NSString stringWithFormat:@"set%@:",[propertyName capitalizedString]]), (IMP)setter, "v@:@");

        //賦值
        [target setValue:value forKey:propertyName];
    }
}

id getter(id self1, SEL _cmd1) {
    NSString *key = NSStringFromSelector(_cmd1);
    Ivar ivar = class_getInstanceVariable([self1 class], "_dictCustomerProperty");  //basicsViewController里面有個_dictCustomerProperty屬性
    NSMutableDictionary *dictCustomerProperty = object_getIvar(self1, ivar);
    return [dictCustomerProperty objectForKey:key];
}

void setter(id self1, SEL _cmd1, id newValue) {
    //移除set
    NSString *key = [NSStringFromSelector(_cmd1) stringByReplacingCharactersInRange:NSMakeRange(0, 3) withString:@""];
    //首字母小寫
    NSString *head = [key substringWithRange:NSMakeRange(0, 1)];
    head = [head lowercaseString];
    key = [key stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:head];
    //移除后綴 ":"
    key = [key stringByReplacingCharactersInRange:NSMakeRange(key.length - 1, 1) withString:@""];

    Ivar ivar = class_getInstanceVariable([self1 class], "_dictCustomerProperty");  //basicsViewController里面有個_dictCustomerProperty屬性
    NSMutableDictionary *dictCustomerProperty = object_getIvar(self1, ivar);
    if (!dictCustomerProperty) {
        dictCustomerProperty = [NSMutableDictionary dictionary];
        object_setIvar(self1, ivar, dictCustomerProperty);
    }
    [dictCustomerProperty setObject:newValue forKey:key];
}

+ (id)getPropertyValueWithTarget:(id)target withPropertyName:(NSString *)propertyName {
    //先判斷有沒有這個屬性，沒有就添加，有就直接賦值
    Ivar ivar = class_getInstanceVariable([target class], [[NSString stringWithFormat:@"_%@", propertyName] UTF8String]);
    if (ivar) {
        return object_getIvar(target, ivar);
    }

    ivar = class_getInstanceVariable([target class], "_dictCustomerProperty");  //basicsViewController里面有個_dictCustomerProperty屬性
    NSMutableDictionary *dict = object_getIvar(target, ivar);
    if (dict && [dict objectForKey:propertyName]) {
        return [dict objectForKey:propertyName];
    } else {
        return nil;
    }
}

優點：這種方法能夠在已有的類中添加property，且能夠遍歷到動態添加的屬性。

 

缺點：比較麻煩，getter和setter需要自己寫，且值也需要自己存儲，如上面的代碼，我是把setter中的值存儲到了_dictCustomerProperty里面，在getter中再從_dictCustomerProperty讀出值。

 

4-通過setValue:forUndefinedKey動態添加鍵值

 

這種方法優點類似property，需要重寫setValue:forUndefinedKey和valueForUndefinedKey:，存值方式也一樣，需要借助一個其它對象。由於這種方式沒通過runtime，所以也比較容易理解。在此就不舉例了。