使用反射的属性类型或类 [英] property type or class using reflection

问题描述

我想知道是否有可能确定Objects属性的类或原始类型.获取所有属性名称和值非常容易. SO答案

I was wondering if it's possible to determine the class or primitive type of an Objects properties. Getting all properties names and values is pretty easy. SO answer

那么当属性没有值或没有nil值时，有什么方法可以获取属性类类型吗?

So is there any way to get the properties class type while the property hast no value or nil value?

示例代码

@interface MyObject : NSObject
@property (nonatomic, copy) NSString *aString;
@property (nonatomic, copy) NSDate *aDate;
@property                   NSInteger aPrimitive;
@end

@implementation MyObject
@synthesize aString;
@synthesize aDate;
@synthesize aPrimitive;

- (void)getTheTypesOfMyProperties {
    unsigned int count;
    objc_property_t* props = class_copyPropertyList([self class], &count);
    for (int i = 0; i < count; i++) {
        objc_property_t property = props[i];

        // Here I can easy get the name or value
        const char * name = property_getName(property);

        // But is there any magic function that can tell me the type?
        // the property can be nil at this time
        Class cls = magicFunction(property);
    }
    free(props);
}

@end

推荐答案

在这样的答案我终于使它起作用了.我只想分享我的结果.

After searching through Apples Documentation about objc Runtime and according to this SO answer I finally got it working. I just want to share my results.

unsigned int count;
objc_property_t* props = class_copyPropertyList([MyObject class], &count);
for (int i = 0; i < count; i++) {
    objc_property_t property = props[i];
    const char * name = property_getName(property);
    NSString *propertyName = [NSString stringWithCString:name encoding:NSUTF8StringEncoding];
    const char * type = property_getAttributes(property);
    NSString *attr = [NSString stringWithCString:type encoding:NSUTF8StringEncoding];

    NSString * typeString = [NSString stringWithUTF8String:type];
    NSArray * attributes = [typeString componentsSeparatedByString:@","];
    NSString * typeAttribute = [attributes objectAtIndex:0];
    NSString * propertyType = [typeAttribute substringFromIndex:1];
    const char * rawPropertyType = [propertyType UTF8String];

    if (strcmp(rawPropertyType, @encode(float)) == 0) {
        //it's a float
    } else if (strcmp(rawPropertyType, @encode(int)) == 0) {
        //it's an int
    } else if (strcmp(rawPropertyType, @encode(id)) == 0) {
        //it's some sort of object
    } else {
        // According to Apples Documentation you can determine the corresponding encoding values
    }

    if ([typeAttribute hasPrefix:@"T@"]) {
        NSString * typeClassName = [typeAttribute substringWithRange:NSMakeRange(3, [typeAttribute length]-4)];  //turns @"NSDate" into NSDate
        Class typeClass = NSClassFromString(typeClassName);
        if (typeClass != nil) {
            // Here is the corresponding class even for nil values
        }
    }

}
free(props);

这篇关于使用反射的属性类型或类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！