Obj-C 实现设计模式 -- 装饰

装饰模式，个人觉得没有太多让人眼前一亮的东西，也或许是现在理解的太过肤浅。

子类通过继承父类对父类（或者接口）进行装饰，改变父类的一些属性，丰富并装饰父类的一些方法。

不多说，贴一贴代码吧。

@interface Beverage : NSObject {
    NSString * _description;
}
- (id) init;
@property (nonatomic, retain) NSString * description;
- (float) cost;
- (NSString *) getDescription;
@end

- (id) init{
    self = [super init];
    if (self) {
        _description = @"Beverage";
    }
    return self;
}
- (float) cost{
    return 0.0;
}
- (NSString *) getDescription{
    return @"Beverage";
}

贴一个子类吧。

@interface Mocha : Beverage {
    Beverage * _beverage;
}
-(id) initWithBverage:(Beverage *) beverage;

- (NSString *) getDescription;
- (float) cost;
@end

@implementation Mocha
-(id) initWithBverage:(Beverage *) beverage{
    
    self = [super init];
    if (self) {
        _beverage = beverage;
    }
    return self;
}
- (NSString *) getDescription{
    return [[_beverage getDescription] stringByAppendingString:@", Mocha"];
}
- (float) cost{
    return 0.80+[_beverage cost];
}
@end

循环调用进行装饰这块还是蛮精彩的。

Beverage * beverage = [[Espresso alloc] init];
    NSLog(@"%@ and %f",[beverage description],[beverage cost]);
    beverage = [[Mocha alloc] initWithBverage:beverage];
    beverage = [[Mocha alloc] initWithBverage:beverage];
    NSLog(@"%@ and %f",[beverage getDescription],[beverage cost]);