面试题：Objective-C中装饰器模式的基本应用

#import <Foundation/Foundation.h>

// 基础图形类
@interface Shape : NSObject
- (void)draw;
@end

@implementation Shape
- (void)draw {
    NSLog(@"绘制图形");
}
@end

// 装饰器基类，继承自Shape
@interface ShapeDecorator : Shape
@property (nonatomic, strong) Shape *decoratedShape;
- (instancetype)initWithShape:(Shape *)shape;
@end

@implementation ShapeDecorator
- (instancetype)initWithShape:(Shape *)shape {
    self = [super init];
    if (self) {
        _decoratedShape = shape;
    }
    return self;
}

- (void)draw {
    [self.decoratedShape draw];
}
@end

// 颜色装饰器
@interface ColorDecorator : ShapeDecorator
@property (nonatomic, strong) NSString *color;
- (instancetype)initWithShape:(Shape *)shape color:(NSString *)color;
@end

@implementation ColorDecorator
- (instancetype)initWithShape:(Shape *)shape color:(NSString *)color {
    self = [super initWithShape:shape];
    if (self) {
        _color = color;
    }
    return self;
}

- (void)draw {
    [super draw];
    NSLog(@"添加颜色: %@", self.color);
}
@end

// 尺寸装饰器
@interface SizeDecorator : ShapeDecorator
@property (nonatomic, assign) CGFloat size;
- (instancetype)initWithShape:(Shape *)shape size:(CGFloat)size;
@end

@implementation SizeDecorator
- (instancetype)initWithShape:(Shape *)shape size:(CGFloat)size {
    self = [super initWithShape:shape];
    if (self) {
        _size = size;
    }
    return self;
}

- (void)draw {
    [super draw];
    NSLog(@"添加尺寸: %.2f", self.size);
}
@end


int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // 创建一个基础图形
        Shape *basicShape = [[Shape alloc] init];
        // 用颜色装饰图形
        ColorDecorator *coloredShape = [[ColorDecorator alloc] initWithShape:basicShape color:@"红色"];
        // 用尺寸装饰已经有颜色的图形
        SizeDecorator *coloredAndSizedShape = [[SizeDecorator alloc] initWithShape:coloredShape size:10.5];
        
        [basicShape draw];
        [coloredShape draw];
        [coloredAndSizedShape draw];
    }
    return 0;
}

上述代码首先定义了基础的Shape类，然后通过ShapeDecorator作为装饰器基类，派生出ColorDecorator和SizeDecorator两个具体的装饰器类，分别为图形添加颜色和尺寸属性。在main函数中展示了如何通过装饰器模式动态地为Shape对象添加不同的装饰。

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面试题：Objective-C中装饰器模式的基本应用

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