Objective-C中的类属性列表 [英] List of class properties in Objective-C

问题描述

有没有办法获得某种类的类属性数组？例如，如果我有这样的接口

Is there a way to get an array of class properties of certain kind? For example if i have interface like this

@interface MyClass : NSObject
    @property (strong,nonatomic) UILabel *firstLabel;
    @property (strong,nonatomic) UILabel *secondLabel;        
@end

我可以在不知道他们的名字的情况下获得对实现中的那些标签的引用吗？

can i get the reference to those labels in implementation without knowing their name?

@implementation MyClass
    -(NSArray*)getListOfAllLabels
    {
            ?????
    }        
@end

我知道我可以用 [NSArray arrayWithObjects：firstLabel，secondLabel，nil] ，但我想做一些类枚举如 for（UILabel * oneLabel in？ ？[self objects] ???）

I know i can do it easily with [NSArray arrayWithObjects:firstLabel,secondLabel,nil], but i would like to do it with some kind of class enumeration like for (UILabel* oneLabel in ???[self objects]???)

推荐答案

动态，运行时观察属性，如果我得到它正确。做这样的事情（在self上实现这个方法，你想要内省的类）：

So more precisely, you want dynamic, runtime observaion of the properties, if I got it correctly. Do something like this (implement this method on self, the class you want to introspect):

#import <objc/runtime.h>

- (NSArray *)allPropertyNames
{
    unsigned count;
    objc_property_t *properties = class_copyPropertyList([self class], &count);

    NSMutableArray *rv = [NSMutableArray array];

    unsigned i;
    for (i = 0; i < count; i++)
    {
        objc_property_t property = properties[i];
        NSString *name = [NSString stringWithUTF8String:property_getName(property)];
        [rv addObject:name];
    }

    free(properties);

    return rv;
}

- (void *)pointerOfIvarForPropertyNamed:(NSString *)name
{
    objc_property_t property = class_getProperty([self class], [name UTF8String]);

    const char *attr = property_getAttributes(property);
    const char *ivarName = strchr(attr, 'V') + 1;

    Ivar ivar = object_getInstanceVariable(self, ivarName, NULL);

    return (char *)self + ivar_getOffset(ivar);
}

使用方法如下：

SomeType myProperty;
NSArray *properties = [self allPropertyNames];
NSString *firstPropertyName = [properties objectAtIndex:0];
void *propertyIvarAddress = [self getPointerOfIvarForPropertyNamed:firstPropertyName];
myProperty = *(SomeType *)propertyIvarAddress;

// Simpler alternative using KVC:
myProperty = [self valueForKey:firstPropertyName];

希望这有帮助。

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