nice helper to code.

Util.h

#import <objc/runtime.h>

//iPhone4's wallpaper size in iOS7
#define kWallpaperSizeNomal CGSizeMake(370.0,598.0)
//iPhone5's wallpaper size in iOS7
#define kWallpaperSizeSpec  CGSizeMake(372.0,696.0)
//esay to get the string value of patameter's name.
#define NameStringOfParam(param) [NSString stringWithFormat:@"%s", #param]
//add accessor(setter getter) for category by define.
#define SYNTHESIZE_CATEGORY_OBJ_PROPERTY(propertyGetter, propertySetter)                                                             \
- (id) propertyGetter {                                                                                                             \
    return objc_getAssociatedObject(self, @selector( propertyGetter ));                                                             \
}                                                                                                                                   \
- (void) propertySetter (id)obj{                                                                                                    \
    objc_setAssociatedObject(self, @selector( propertyGetter ), obj, OBJC_ASSOCIATION_RETAIN_NONATOMIC);                            \
}
 
 
#define SYNTHESIZE_CATEGORY_VALUE_PROPERTY(valueType, propertyGetter, propertySetter)                                                \
- (valueType) propertyGetter {                                                                                                      \
    valueType ret = {0};                                                                                                                  \
    [objc_getAssociatedObject(self, @selector( propertyGetter )) getValue:&ret];                                                    \
    return ret;                                                                                                                     \
}                                                                                                                                   \
- (void) propertySetter (valueType)value{                                                                                           \
    NSValue *valueObj = [NSValue valueWithBytes:&value objCType:@encode(valueType)];                                                \
    objc_setAssociatedObject(self, @selector( propertyGetter ), valueObj, OBJC_ASSOCIATION_RETAIN_NONATOMIC);                       \
}