控件功能：

在View上嵌一个控件，从服务器获得defaultNumber，在页面加载后默认显示，然后按"+"，个数增加；按"-"，个数减少。在个数小于minNumber时，"-"按钮不可用。

控件实现

新建一个类numberSelectView，继承UIView。控件都是在xib文件中使用，需要实现-(id)initWithCoder方法进行初始化。调用类和numberSelectView类的点击事件的关联，用协议和代理实现。

代码

代码最直接了
.h文件

#import <UIKit/UIKit.h>

@class NumberSelectView;

@protocol NumberSelectViewDelegate <NSObject>

-(void)numberSelectView:(NumberSelectView*)numberSelectView currentNumber:(NSInteger)currentNumber;
@ender 
@interface NumberSelectView : UIView
//服务器获得的数字
@property (nonatomic, assign) NSInteger defaultNumber;
//选择的最小值
@property (nonatomic, assign) NSInteger minNumber;
//当前显示的数字
@property (nonatomic, assign) NSInteger currentNumber;

@property (nonatomic, assign) id<NumberSelectViewDelegate> delegate;

@end

.m文件

#import "NumberSelectView.h"

@interface NumberSelectView()

@property (nonatomic, strong) UILabel *numberLabel;
@property (nonatomic, strong) UIButton *cutButton;
@end

@implementation NumberSelectView

-(id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super initWithCoder:aDecoder]) {
        self.backgroundColor = [UIColor clearColor];
        [self setView:self.frame];
    }
    return self;
}

-(void)setView:(CGRect)frame
{
    UIButton* addButton = [UIButton buttonWithType:UIButtonTypeCustom];
    addButton.frame = CGRectMake(frame.size.width/2 + 15, 0, frame.size.width/2 - 15, frame.size.height);
    addButton.titleLabel.font = [UIFont systemFontOfSize:22];
    [addButton setTitle:@"+" forState:UIControlStateNormal];
    [addButton setBackgroundImage:[UIImage imageWithColor:[UIColor WhiteColor] cornerRadius:5] forState:UIControlStateNormal];
    [addButton addTarget:self action:@selector(addNumber:) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:addButton];
    _cutButton = [UIButton buttonWithType:UIButtonTypeCustom];
    _cutButton.frame = CGRectMake(0, 0, frame.size.width/2 - 15, frame.size.height);
    _cutButton.titleLabel.font = [UIFont systemFontOfSize:22];
    [_cutButton setTitle:@"-" forState:UIControlStateNormal];
    [_cutButton setBackgroundImage:[UIImage imageWithColor:[UIColor grayColor] cornerRadius:5] forState:UIControlStateNormal];
    [_cutButton addTarget:self action:@selector(cutNumber:) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:_cutButton];

    _numberLabel = [[UILabel alloc] initWithFrame:CGRectMake(frame.size.width/2 - 15, 0, 30, frame.size.height)];
    _numberLabel.backgroundColor = [UIColor clearColor];
    _numberLabel.font = [UIFont systemFontOfSize:14];
    _numberLabel.textColor = [UIColor darkGrayColor];
    _numberLabel.textAlignment = NSTextAlignmentCenter;
    _numberLabel.text = @"0";
    [self addSubview:_numberLabel];
}

-(void)setDefaultNumber:(NSInteger)defaultNumber
{
    _currentNumber = defaultNumber;
    [_cutButton setEnabled:_currentNumber>_minNumber];
    _numberLabel.text = [NSString stringWithFormat:@"%d",defaultNumber];
}

-(void)setMinNumber:(NSInteger)minNumber
{
    _minNumber = minNumber;
    [_cutButton setEnabled:_currentNumber>_minNumber];
}

-(void)setCurrentNumber:(NSInteger)currentNumber
{
    _currentNumber = currentNumber;
    [_cutButton setEnabled:_currentNumber>_minNumber];
    _numberLabel.text = [NSString stringWithFormat:@"%d",_currentNumber];
}

- (void)addNumber:(UIButton*)addButton
{
    _currentNumber++;
    _numberLabel.text = [NSString stringWithFormat:@"%d",_currentNumber];
    if (_delegate != nil && [_delegate respondsToSelector:@selector(numberSelectView:currentNumber:)]) {
        [_delegate numberSelectView:self currentNumber:_currentNumber];
    }
    [_cutButton setEnabled:(_currentNumber > _minNumber)];
}

- (void)cutNumber:(UIButton*)cutButton
{
    _currentNumber--;
    _numberLabel.text = [NSString stringWithFormat:@"%d",_currentNumber];
    if (_delegate != nil && [_delegate respondsToSelector:@selector(numberSelectView:currentNumber:)]) {
        [_delegate numberSelectView:self currentNumber:_currentNumber];
    }
    [cutButton setEnabled:!(_minNumber == _currentNumber)];
}

@end

在用到该View的类里，在delegate方法里写具体事件。