这个项目是在xcode中运行的，当运行时总是无法成功，提示for循环的问题（i等于一个负数）!代码如下，有问题的代码用红字标出，请各位帮忙看一下，谢谢了！ 
#import <Foundation/Foundation.h>

typedef enum{
    kCircle,
    kRectangle,
    kEgg
}ShapeType;

typedef enum{
    kRedColor,
    kGreenColor,
    kBlueColor
}ShapeColor;

typedef struct{
    int x,y,width,height;
}ShapeRect;

typedef struct{
    ShapeType type;
    ShapeColor fillColor;
    ShapeRect bounds;
}shape;

//返回颜色的值
NSString *colorName(ShapeColor fillColor){
    
    switch(fillColor){
        case kRedColor:
            return (@”red”);
            break;
        case kGreenColor:
            return (@”Green”);
            break;
        case kBlueColor:
            return (@”Blue”);
            break;
    }
    
}

//声明Circle
@interface Circle:NSObject{
    @private
    ShapeRect bounds;
    ShapeColor fillColor;
}

-(void)setBounds:(ShapeRect) bounds;
-(void)setColor:(ShapeColor) fillColor;
-(void)draw;
@end

//声明Rectangle
@interface Rectangle:NSObject{
@private
    ShapeRect bounds;
    ShapeColor fillColor;
}

-(void)setBounds:(ShapeRect) bounds;
-(void)setColor:(ShapeColor) fillColor;
-(void)draw;
@end

//声明Egg
@interface Egg:NSObject{
@private
    ShapeRect bounds;
    ShapeColor fillColor;
}

-(void)setBounds:(ShapeRect) bounds;
-(void)setColor:(ShapeColor) fillColor;
-(void)draw;
@end

//实现Circle
@implementation Circle

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

-(void)setColor:(ShapeColor)c{
    fillColor=c;
}

-(void)draw{
    NSLog(@”\ndrawing a circle at(%d,%d,%d,%d) in %@\n”,
          bounds.x,bounds.y,bounds.width,bounds.height,colorName(fillColor));
}
@end

//实现Rectangle
@implementation Rectangle

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

-(void)setColor:(ShapeColor)c{
    fillColor=c;
}

-(void)draw{
    NSLog(@”\ndrawing a Rectangle at(%d,%d,%d,%d) in %@\n”,
          bounds.x,bounds.y,bounds.width,bounds.height,colorName(fillColor));
}
@end

//实现Egg
@implementation Egg

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

-(void)setColor:(ShapeColor)c{
    fillColor=c;
}

-(void)draw{
    NSLog(@”\ndrawing a Egg at(%d,%d,%d,%d) in %@\n”,
          bounds.x,bounds.y,bounds.width,bounds.height,colorName(fillColor));
}
@end

//实例化对象
void drawShapes(id shapes[],int count){
    
    for(int i=0;i<count;i++){
        id shape=shapes[i];
        [shape draw];
    }
    
}

int main(int agrc,const char *argv[]){
    id shapes[3];
    
    ShapeRect bounds0={0,0,10,30};
    shapes[0]=[Circle new];
    [shapes[0] setBounds:bounds0];
    [shapes[0] setColor:kRedColor];
    
    ShapeRect bounds1={30,40,50,60};
    shapes[1]=[Rectangle new];
    [shapes[1] setBounds:bounds1];
    [shapes[1] setColor:kGreenColor];
    
    ShapeRect bounds2={15,18,37,29};
    shapes[2]=[Egg new];
    [shapes[2] setBounds:bounds2];
    [shapes[2] setColor:kBlueColor];
    
    drawShapes(shapes, 3);
    return (0);
}