简单?工?厂模式 (Simple Factory Pattern)

@interface ViewController ()
{
    Shape *_shape;
}

@end

@implementation ViewController

- (void)loadView
{
    //设置画板
    self.view=[[SimpleDrawBoard alloc]init];
    self.view.backgroundColor=[UIColor whiteColor];
}
- (void)viewDidLoad {
    [super viewDidLoad];

}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch=[touches anyObject];
    CGPoint point=[touch locationInView:self.view];
    //工厂生产形状
    _shape=[Factory shapeWithType:kRud];
//    _shape.fillColor=[UIColor blackColor];
    [_shape addPoint:point];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch=[touches anyObject];
    CGPoint point=[touch locationInView:self.view];
    SimpleDrawBoard *board=(SimpleDrawBoard *)self.view;
    [_shape addPoint:point];
    [board drawShape:_shape];
}

 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch=[touches anyObject];
    CGPoint point=[touch locationInView:self.view];
    [_shape addPoint:point];
    SimpleDrawBoard *board=(SimpleDrawBoard *)self.view;
    [board drawShape:_shape];
}

//
//  SimpleDrawBoard.m
//  Facetory-0904
//
//  Created by apple on 14-9-4.
//  Copyright (c) 2014年 apple. All rights reserved.
//

#import "SimpleDrawBoard.h"
@interface SimpleDrawBoard()
{
    Shape *_shape;
}
@end

@implementation SimpleDrawBoard

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    CGContextRef context=UIGraphicsGetCurrentContext();
    [_shape draw:context];
}

- (void)drawShape:(Shape *)shape
{
    _shape=shape;
    [self setNeedsDisplay];
}

@end

//
//  Shape.m
//  Facetory-0904
//
//  Created by apple on 14-9-4.
//  Copyright (c) 2014年 apple. All rights reserved.
//

#import "Shape.h"

@implementation Shape

- (void)addPoint:(CGPoint)point
{
    [self doesNotRecognizeSelector:_cmd];
}

- (void)draw:(CGContextRef)context
{
    if (_fillColor)
    {
        [_fillColor setFill];
    }
    if (_lineWidth)
    {
        CGContextSetLineWidth(context, _lineWidth);
    }
    if (_strokColor)
    {
        [_strokColor setStroke];
    }
}
@end

//
//  Rud.m
//  SimpleDrawBoard
//
//  Created by apple on 14-9-4.
//  Copyright (c) 2014年 戴维营教育. All rights reserved.
//

#import "Rud.h"
#include "math.h"

@interface Rud ()
{
    CGPoint _startPoint;
    CGPoint _endPoint;
    CGFloat rid;
    BOOL bEnd;
}
@end

@implementation Rud
- (void)addPoint:(CGPoint)position
{
    if (!bEnd) {
        _startPoint = position;
        bEnd = YES;
    }
    else {
        _endPoint = position;
        CGFloat r=(_endPoint.x - _startPoint.x)*(_endPoint.x - _startPoint.x)+(_endPoint.y - _startPoint.y)*(_endPoint.y - _startPoint.y);
        rid=sqrtf(r);
    }
}

- (void)draw:(CGContextRef)context
{
    [super draw:context];
    CGRect rect = CGRectMake(_startPoint.x-rid, _startPoint.y-rid,rid*2,rid*2);

    CGContextAddEllipseInRect(context, rect);
    CGContextDrawPath(context, kCGPathEOFillStroke);
}
@end