objective-C 的OOP(上)--类定义、继承及方法调用

上一篇展示了如何用传统的“面向过程编程方法”，实现画“矩形”、“圆”、“椭圆”，这一篇看下如何改用OOP的方法来实现：

因为要用到“颜色”以及“矩形区域”二个枚举，先把他们抽出来单独放在CommDef.h文件中

//定义“几何形状颜色”枚举
typedef enum
{
	kRedColor,
	kGreenColor,
	kBlueColor
} ShapeColor;

//定义“几何形状矩形区域”结构
typedef struct
{
	int x,y,width,height;
} ShapeRect;

然后再定义基类Shape，注意：在obj-C中，定义一个类通常分成二部分，一部分是".h"的文件，用来申明类有哪些成员（也称为类的定义文件，类似于接口），另一部分是".m"的文件，用来提供具体实现

Shape类的申明部分如下:(Shape.h)

//
//  Shape.h
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "CommDef.h"

@interface Shape : NSObject {
	ShapeColor fillColor;
	ShapeRect bounds;	
}

- (void) setFillColor:(ShapeColor) fillColor;
- (void) setBounds:(ShapeRect) bounds;
- (void) draw;
- (NSString*) getColorName:(ShapeColor) fillColor;

@end //Shape

Shape类的实现部分如下:(Shape.m)

//
//  Shape.m
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Shape.h"


@implementation Shape

- (void) setBounds:(ShapeRect)b
{
	bounds = b;
}

- (void) setFillColor:(ShapeColor)f
{
	fillColor =f;
}

//注：这个方法留给子类去实现，所以这里只要一个空壳就行了
- (void) draw
{
	
}


- (NSString*) getColorName:(ShapeColor)f
{
	
	switch (f) {
		case kRedColor:
			return @"red";
			break;
		case kGreenColor:
			return @"green";
			break; 
		case kBlueColor:
			return @"blue";
			break; 
		default:
			return @"no clue";
			break;
	}
	
}

@end

语法有点奇怪，初次接触，只能强迫自己忘记吧。

然后定义子类Circle

申明部分Circle.h

//
//  Circle.h
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Shape.h"
//注：因为Circle类不需要扩展其它方法，所以这里也只要一个空壳
@interface Circle : Shape {

}

@end

实现部分Circle.m

//
//  Circle.m
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Circle.h"


@implementation Circle

-(void) draw
{
	NSLog(@"drawing a Cirle at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end

注：上面展示了在obj-C中如何调用父类的方法[super getColorName:fillColor]

子类Rectangle

//
//  Rectangle.h
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Shape.h"

@interface Rectangle : Shape {

}

@end

实现部分

//
//  Rectangle.m
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Rectangle.h"


@implementation Rectangle
-(void) draw
{
	NSLog(@"drawing a Rectangle at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end

子类Ellipse

//
//  Ellipse.h
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//


#import "Shape.h"

@interface Ellipse : Shape{

}
@end

实现部分

//
//  Ellipse.m
//  HelloWorld
//
//  Created by jimmy.yang on 11-1-26.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Ellipse.h"


@implementation Ellipse
-(void) draw
{
	NSLog(@"drawing a ellipse at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end

最后看下调用的主函数HelloWorld.m

#import "CommDef.h"
#import "Circle.h"
#import "Rectangle.h"
#import "Ellipse.h"

int main (int argc, const char * argv[]) {    
	
	id shape[2] ;
	
	ShapeRect rect0 =  {0,0,10,30};
	shape[0] = [Circle new];
	[shape[0] setBounds:rect0];
	[shape[0] setFillColor:kGreenColor];
	[shape[0] draw];	
	
	ShapeRect rect1 =  {0,0,40,50};
	shape[1] = [Rectangle new];
	[shape[1] setBounds:rect1];
	[shape[1] setFillColor:kRedColor];
	[shape[1] draw];

	
	ShapeRect rect2 =  {0,0,30,30};
	shape[2] = [Ellipse new];
	[shape[2] setBounds:rect2];
	[shape[2] setFillColor:kBlueColor];
	[shape[2] draw];

	
    return 0;
}

注：上面的代码中有一个id的变量，在obj-C中id相当于“任意类型”，意为指向某对象的指针（哪怕你不知道这个对象是什么类型），总之，如果你不知道某对象的具体类型时，用它就对了。同时我们也看到了，创建一个类的实例用“[类 new]”来完成。

最后附上文件结构图: