objective-c中通过类的属性的名字获取属性的类型（谢绝转载）

（谢绝转载）

最近想自己写一个直接从字典解析为模型类的库，其中遇到的最大的问题是怎么通过类的属性的名字这个字符串得出这个属性的类型，是int还是

NSString获取他的类型。以方便赋值。

自己也去http://stackoverflow.com/上面提了个问题

How to know the type of class's property from string? 英文水平不过关啊，有的老外直接回答让我表达的清楚点，他不明白我的问题，那个汗啊。

不过通过热心的网友帮助，很快的得到了解答。所以写篇博客记录一下。

通过Objective-C Runtime函数这个问题得到了很好的解决。

总的来说呢就是通过下面两个函数：

objc_property_t* props = class_copyPropertyList([TestModelclass], &count);

这个可以获得一个类的所有属性的一个数组。

const char * type =property_getAttributes(property);

这个函数可以获得属性的类型。

需要的头文件有

#import <objc/message.h>
#import <objc/runtime.h>

大概的代码如下：

    unsigned int count;
    objc_property_t* props = class_copyPropertyList([TestModel 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@"] && [typeAttribute length] > 1) {
            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);

另一种方法是自己去实现获取属性类型的方法

//获取属性名称数组
- (NSDictionary *)classPropsFor:(Class)klass
{
    if (klass == NULL) {
        return nil;
    }
    
    NSMutableDictionary *results = [[NSMutableDictionary alloc] init];
    
    unsigned int outCount, i;
    objc_property_t *properties = class_copyPropertyList(klass, &outCount);
    for (i = 0; i < outCount; i++) {
        objc_property_t property = properties[i];
        const char *propName = property_getName(property);
        if(propName) {
            const char *propType = getPropertyType(property);
            NSString *propertyName = [NSString stringWithUTF8String:propName];
            NSString *propertyType = [NSString stringWithUTF8String:propType];
            
            NSLog(@"propertyName %@ propertyType %@", propertyName, propertyType);
            
            [results setObject:propertyType forKey:propertyName];
        }
    }
    free(properties);
    
    // returning a copy here to make sure the dictionary is immutable
    return [NSDictionary dictionaryWithDictionary:results];
}
//获取属性的方法
static const char *getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    //printf("attributes=%s\n", attributes);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T' && attribute[1] != '@') {
            // it's a C primitive type:
            
            // if you want a list of what will be returned for these primitives, search online for
            // "objective-c" "Property Attribute Description Examples"
            // apple docs list plenty of examples of what you get for int "i", long "l", unsigned "I", struct, etc.
            
            NSString *name = [[NSString alloc] initWithBytes:attribute + 1 length:strlen(attribute) - 1 encoding:NSASCIIStringEncoding];
            return (const char *)[name cStringUsingEncoding:NSASCIIStringEncoding];
        }
        else if (attribute[0] == 'T' && attribute[1] == '@' && strlen(attribute) == 2) {
            // it's an ObjC id type:
            return "id";
        }
        else if (attribute[0] == 'T' && attribute[1] == '@') {
            // it's another ObjC object type:
            NSString *name = [[NSString alloc] initWithBytes:attribute + 3 length:strlen(attribute) - 4 encoding:NSASCIIStringEncoding];
            return (const char *)[name cStringUsingEncoding:NSASCIIStringEncoding];
        }
    }
    return "";
}