Question

我有一个基本的Point包装类：

@interface Point : NSObject
@property (nonatomic) CGPoint point;
- (instancetype)initWithPoint:(CGPoint)point;
@end

由Line s：

定义的Point类

@interface Line : NSObject
@property (nonatomic, strong) Point startPoint;
@property (nonatomic, strong) Point endPoint;
+ (NSArray *)linesConnectingPoints:(NSArray *)points;
- (instancetype)initWithStartPoint:(Point)startPoint endPoint:(Point)endPoint;
@end

linesConnectingPoints:是一种方便的方法，用于创建将点数组连接在一起的行数组（因此，如果您有4个Point的数组，则调用linesConnectingPoints:可能会创建一个4 Line s的数组，表示四边形的边。）

@implementation Line

+ (NSArray *)linesConnectingPoints:(NSArray *)points
{
    NSMutableArray *lines = [[NSMutableArray alloc] initWithCapacity:points.count];
    int i;
    for (i = 0; i < points.count - 1; i++)
    {
        lines[i] = [[self alloc] initWithStartPoint:points[i] endPoint:points[i+1];
    }
    // The final line connects the last point and the first point
    lines[i] = [[self alloc] initWithStartPoint:points[i] endPoint:points[0]];
    return lines;
}
...
@end

现在我想创建一个名为Line的{{1}}子类，它添加了一个额外的线条粗细属性：

ThickLine

@interface ThickLine : Line @property (nonatomic) float thickness; - (instancetype)initWithStartPoint:(Point)startPoint endPoint:(Point)endPoint thickness:(float)thickness; @end成为指定的初始化程序，如下所示：

initWithStartPoint:endPoint:thickness

现在我可以致电// Overriding the superclass' designated initializer - (instancetype)initWithStartPoint:(Point)startPoint endPoint:(Point)endPoint { return [self initWithStartPoint:startPoint endPoint:endPoint thickness:1]; } - (instancetype)initWithStartPoint:(Point)startPoint endPoint:(Point)endPoint thickness:(float)thickness { self = [super initWithStartPoint:startPoint endPoint:endPoint]; if (self) { _thickness = thickness; } return self; }，我会得到NSArray *thickLines = [ThickLine linesConnectingPoints:somePoints];个数组，每个ThickLine等于1。

但是，如果我想指定厚度怎么办？我可以编写一个方法thickness并将其粘贴在linesConnectingPoints:withThickness:中，如此：

ThickLine.m

但这看起来与我已编写的超类'+ (NSArray *)linesConnectingPoints:(NSArray *)points withThickness:(float)thickness { NSMutableArray *lines = [[NSMutableArray alloc] initWithCapacity:points.count]; int i; for (i = 0; i < points.count - 1; i++) { lines[i] = [[self alloc] initWithStartPoint:points[i] endPoint:points[i+1] thickness:thickness; } lines[i] = [[self alloc] initWithStartPoint:points[i] endPoint:points[0] thickness:thickness]; return lines; }方法完全相同，只是使用了不同的初始值设定项。

当然，这里的重复是微不足道的，并不是什么大问题，但如果我想创建lineConnectingPoints:的多个其他子类呢？我可能有Line，ColoredLine，LabeledLine等等，而且我必须为每个子类重写这个“便捷方法”（FancyLine for { {1}}，linesConnectingPoints:withColor:为ColoredLine，linesConnectingPoints:withText:为LabeledLine，等等。每个便捷方法都与超类的原始方法完全相同，但初始化器中使用的参数除外。

有没有办法减少这里的重复？有些方法可以将重复的代码封装在一个单独的函数中，并且能够指定使用的初始化程序吗？

Answer 1

这样怎么样？

行：

typedef Line *(^LineFactoryBlock_t)(Point *startPoint, Point *endPoint);

@implementation Line
+(NSArray *)linesConnectingPoints:(NSArray *)points {
    return [self linesConnectingPoints:points withFactoryBlock:^Line *(Point *startPoint, Point *endPoint) {
        return [[self alloc] initWithStartPoint:startPoint endPoint:endPoint];
    }];
}

+(NSArray *)linesConnectingPoints:(NSArray *)points withFactoryBlock:(LineFactoryBlock_t)factory {
    NSMutableArray *lines = [[NSMutableArray alloc] initWithCapacity:points.count];
    int i;

    for (i = 0; i < points.count - 1; i++) {
        lines[i] = factory(points[i], points[i+1]);
    }
    // The final line connects the last point and the first point
    lines[i] = factory(points[i], points[0]);
    return lines;
}
//...
@end

ThickLine：

+(NSArray *)linesConnectingPoints:(NSArray *)points withThickness:(float)thickness {
    return [self linesConnectingPoints:points withFactoryBlock:^Line *(Point *startPoint, Point *endPoint) {
        return [[self alloc] initWithStartPoint:startPoint endPoint:endPoint thickness:thickness];
    }];
};

减少类方法继承的重复

1 个答案: