一:

在界面上拖入相应的控件

二: 给每个控件设置关联

//监听按钮的点击

- (IBAction)compute:(id)sender;

//第一个文本输入框的值

@property (weak, nonatomic) IBOutlet UITextField *numField1;

@property (weak, nonatomic) IBOutlet UITextField *numField2;

@property (weak, nonatomic) IBOutlet UILabel *totalLabel;

三: 处理按钮点击事件

- (IBAction)compute:(id)sender {

//1 取得两个文本输入框的值

NSString *text1 = self.numField1.text;

NSString *text2 = self.numField2.text;

//2 相减

int deffernece = 0;

int num1 = [text1 intValue];

int num2 = [text2 intValue];

if(num1 > num2 || num1 == num2){

deffernece = num1 - num2;

}else{

//弹框

//创建一个弹框

//initWithTitle 标题

//message 详细信息

//delegate 代理

//cancelButtonTitle 取消按钮的文字

//otherButtonTitles 其他按钮的文字

UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"提示" message:@"输入的数字不合理" delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:nil, nil];

//2.2显示

[alert show];

}

//3 把结果显示在右边的文本标签中

_totalLabel.text = [NSString stringWithFormat:@"%d",deffernece];

[self.view endEditing:YES];

}