• Objective-C中的面向对象编程


    1.过程式编程实例,画出Shape数组中的图形:

    //
    //  main.m
    //  hello-obj
    //
    //  Created by zhouyang on 16/4/4.
    //  Copyright © 2016年 zhouyang. All rights reserved.
    //
    #import <Foundation/Foundation.h>
    //枚举变量,代表形状
    typedef enum{
        kCircle,
        kRectangle,
        kEgg
    } ShapeType;
    //枚举变量,代表颜色
    typedef enum{
        kRedColor,
        kGreenColor,
        kBlueColor
    } ShapeColor;
    //结构体,代表形状
    typedef struct{
        int x,y,width,height;
    }ShapeRect;
    //结构体,表示多边形的各项属性
    typedef struct {
        ShapeType type;
        ShapeColor fillColor;
        ShapeRect bounds;
        
    }Shape;
    //返回颜色对应的NSString
    NSString *colorName(ShapeColor colorName){
        switch(colorName){
            case kRedColor:
                return @"red";
                break;
            case kGreenColor:
                return @"green";
                break;
            case kBlueColor:
                return @"blue";
                break;
        }
        return @"no clue";
    }
    //“画出”圆,其实就是输出图形的各项属性
    void drawCircle(ShapeRect bounds,ShapeColor fillColor){
        NSLog(@"drawing a circle at (%d,%d,%d,%d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              colorName(fillColor)
        );
    }
    //“画出”长方形
    void drawRectangle(ShapeRect bounds,ShapeColor fillColor){
        NSLog(@"drawing a rectangle at (%d,%d,%d,%d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              colorName(fillColor)
        );
    }
    //"画出"Egg
    void drawEgg(ShapeRect bounds,ShapeColor fillColor){
        NSLog(@"drawing a egg at (%d,%d,%d,%d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              colorName(fillColor)
        );
    }
    //遍历Shape数组,画出对应的图形
    void drawShapes(Shape shapes[],int count){
        for(int i=0;i<count;i++){
            switch (shapes[i].type) {
                case kCircle:
                    drawCircle(shapes[i].bounds, shapes[i].fillColor);
                    break;
                case kRectangle:
                    drawRectangle(shapes[i].bounds,shapes[i].fillColor);
                    break;
                case kEgg:
                    drawEgg(shapes[i].bounds,shapes[i].fillColor);
                    break;
                    
                default:
                    NSLog(@"can't find the shape!");
            }
            
        }
    }
    int main(int argc, const char * argv[]) {
        Shape shapes[3];
        //Circle
        ShapeRect rect0={0,0,10,30};
        shapes[0].type=kCircle;
        shapes[0].fillColor=kRedColor;
        shapes[0].bounds=rect0;
        //Rectangle
        ShapeRect rect1={30,40,50,60};
        shapes[1].type=kRectangle;
        shapes[1].fillColor=kGreenColor;
        shapes[1].bounds=rect1;
        //Egg
        ShapeRect rect2={15,18,37,29};
        shapes[2].type=kEgg;
        shapes[2].fillColor=kBlueColor;
        shapes[2].bounds=rect2;
        //画出数组Shape中的图形
        drawShapes(shapes,3);
    }

      基于OOP编程,可以将上述代码改写为以下格式:

    #import <Foundation/Foundation.h>
    //注意枚举变量的定义,变量之间以逗号隔开
    typedef enum{
        kRedColor,
        kGreenColor,
        kBlueColor
    }ShapeColor;
    typedef struct {
        int x,y,width,height;
    }ShapeRect;
    NSString *ColorName(ShapeColor color){
        switch (color) {
            case kRedColor:
                return @"red";
                break;
            case kGreenColor:
                return @"green";
                break;
            case kBlueColor:
                return @"blue";
                break;
        }
         return @"no clue";
    }
    //定义接口
    //@告诉编译器,这里是对C的扩展
    @interface Circle:NSObject{
        //定义数据成员
        @private
        ShapeColor fillColor;
        ShapeRect bounds;
    }
    //列举方法的名称,返回值的类型和某些参数
    //前面的短线表明这是Objective-c方法的声明
    - (void) setFillColor:(ShapeColor) fillColor;
    - (void) setBounds:(ShapeRect) bounds;
    - (void) draw;
    @end //@Circle
    //接口定义完毕
    //下面开始实现接口Circle
    @implementation Circle
    - (void) setFillColor:(ShapeColor) c {
        fillColor=c;
    }//设置颜色
    - (void) setBounds:(ShapeRect) b{
        bounds=b;
    }
    - (void) draw{
        NSLog(@"drawing a circle at (%d %d %d %d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              ColorName(fillColor)
              );
    }
    @end //Circle
    //定义接口
    //@告诉编译器,这里是对C的扩展
    @interface Rectangle:NSObject{
        //定义数据成员
    @private
        ShapeColor fillColor;
        ShapeRect bounds;
    }
    //列举方法的名称,返回值的类型和某些参数
    //前面的短线表明这是Objective-c方法的声明
    - (void) setFillColor:(ShapeColor) fillColor;
    - (void) setBounds:(ShapeRect) bounds;
    - (void) draw;
    @end //@Rectangle
    //接口定义完毕
    //下面开始实现接口Rectangle
    @implementation Rectangle
    - (void) setFillColor:(ShapeColor) c {
        fillColor=c;
    }//设置颜色
    - (void) setBounds:(ShapeRect) b{
        bounds=b;
    }
    - (void) draw{
        NSLog(@"drawing a rectangle at (%d %d %d %d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              ColorName(fillColor)
              );
    }
    @end //Egg
    //定义接口
    //@告诉编译器,这里是对C的扩展
    @interface Egg:NSObject{
        //定义数据成员
    @private
        ShapeColor fillColor;
        ShapeRect bounds;
    }
    //列举方法的名称,返回值的类型和某些参数
    //前面的短线表明这是Objective-c方法的声明
    - (void) setFillColor:(ShapeColor) fillColor;
    - (void) setBounds:(ShapeRect) bounds;
    - (void) draw;
    @end //@Triangle
    //接口定义完毕
    //下面开始实现接口Triangle
    @implementation Egg
    - (void) setFillColor:(ShapeColor) c {
        fillColor=c;
    }//设置颜色
    - (void) setBounds:(ShapeRect) b{
        bounds=b;
    }
    - (void) draw{
        NSLog(@"drawing a egg at (%d %d %d %d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              ColorName(fillColor)
              );
    }
    @end //Egg
    //定义接口
    //@告诉编译器,这里是对C的扩展
    @interface Triangle:NSObject{
        //定义数据成员
    @private
        ShapeColor fillColor;
        ShapeRect bounds;
    }
    //列举方法的名称,返回值的类型和某些参数
    //前面的短线表明这是Objective-c方法的声明
    - (void) setFillColor:(ShapeColor) fillColor;
    - (void) setBounds:(ShapeRect) bounds;
    - (void) draw;
    @end //@Triangle
    //接口定义完毕
    //下面开始实现接口Triangle
    @implementation Triangle
    - (void) setFillColor:(ShapeColor) c {
        fillColor=c;
    }//设置颜色
    - (void) setBounds:(ShapeRect) b{
        bounds=b;
    }
    - (void) draw{
        NSLog(@"drawing a triangle at (%d %d %d %d) in %@",
              bounds.x,
              bounds.y,
              bounds.width,
              bounds.height,
              ColorName(fillColor)
              );
    }
    @end //Triangle
    //画出图形
    //id 对应类实例
    void drawShapes(id shapes[],int count){
        for(int i=0;i<count;i++){
            id shape=shapes[i];
            [shape draw];
        }
    }
    int main(int argc, const char * argv[]) {
        
        id shapes[4];
        //Circle
        shapes[0]=[Circle new];//这里创建新的类实例将new加在类名称的后面
        ShapeRect rect0={0,0,10,30};
        [shapes[0] setBounds:rect0];
        [shapes[0] setFillColor:kRedColor];
        //Rectangle
        ShapeRect rect1={30,40,50,60};
        shapes[1] =[ Rectangle new];
        [shapes[1] setBounds:rect1];
        [shapes[1] setFillColor:kGreenColor];
        //Egg
        ShapeRect rect2={15,18,37,29};
        shapes[2] =[Egg new];
        [shapes[2] setBounds:rect2];
        [shapes[2] setFillColor:kBlueColor];
        //Triangle
        ShapeRect rect3 ={47,32,80,50};
        shapes[3] =[Triangle new];
        [shapes[3] setBounds:rect3];
        [shapes[3] setFillColor:kGreenColor];
        //画出数组Shape中的图形
        drawShapes(shapes,4);
        return 0;
    }

        可见利用OOP编程方式,增加新的图形更加简单,修改的地方更少。

        请注意object-c中的接口,类的定义以及类方法的调用,这里与C++还是存在很多的不同。

        可能会遇到错误:Must explicitly describe intended ownership of an object array parameter,解决方法如下:

      

        将Objective-c Automatic Reference Counting 设置为No,关闭ARC即可。

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  • 原文地址:https://www.cnblogs.com/zhoudayang/p/5357554.html
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