仅在文本框输入后启用按钮：苹果App拒审及代码问题求助

• 我的App此前多年通过审核，近期被苹果拒绝
• App包含两个UITextField（用于输入姓氏、名字），点击Go按钮提交内容
• 苹果反馈直接点击Go按钮会导致App崩溃，但我本地测试仅会弹出错误提示No name - please reenter
• 为满足审核要求，我修改了文本框编辑方法（代码如下），但始终无法实现「仅当两个输入框都有内容时才启用Go按钮」的需求

// Text Field methods

-(void)textFieldDidBeginEditing:(UITextField *)textField {
    
    UIFont* boldFont = [UIFont fontWithName:@"Helvetica-Bold" size: 24];
    
    if (textField == _lastName) {
        [_lastName becomeFirstResponder];
        [_lastName setFont:boldFont];
        _lastName.autocorrectionType = UITextAutocorrectionTypeNo;;
        _lastName.autocapitalizationType = UITextAutocapitalizationTypeNone;
        _lastName.text = @"";
        
        NSLog(@"user editing last...");
        
        // Enable button once fields have values
            
        if ([_lastName.text isEqual: @""] && [_firstName.text  isEqual: @""])
            {
                _fwdButton.enabled = YES;
            }
        
    }
    
    else {
        [_firstName becomeFirstResponder];
        [_firstName setFont:boldFont];
        _firstName.autocorrectionType = UITextAutocorrectionTypeNo;;
        _firstName.autocapitalizationType = UITextAutocapitalizationTypeNone;
        _firstName.text = @"";
        
        NSLog(@"user editing first");
        
        // Enable button once fields have values
            
        if ([_lastName.text isEqual: @""] && [_firstName.text  isEqual: @""])
            {
                _fwdButton.enabled = YES;
            }
    }
    
}

1. 触发时机错误：按钮状态判断放在textFieldDidBeginEditing方法中，该方法仅在用户开始编辑文本框时触发，无法实时响应输入内容的变化（比如输入后删除、切换输入框等场景）
2. 逻辑判断完全颠倒：当前条件是「两个输入框都为空时启用按钮」，和需求「有内容才启用」完全相反
3. 冗余操作：[textField becomeFirstResponder]是多余的（进入该方法时文本框已是第一响应者）；每次开始编辑就清空文本框的逻辑也会影响用户体验
4. 崩溃隐患未根除：即使按钮启用逻辑修复，仍需在点击方法中增加校验，避免极端情况导致崩溃

1. 绑定文本框内容变化事件 #

在viewDidLoad中给两个UITextField添加editingChanged事件监听，实时响应内容变化：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 绑定文本框内容变化事件
    [_lastName addTarget:self action:@selector(textFieldTextChanged:) forControlEvents:UIControlEventEditingChanged];
    [_firstName addTarget:self action:@selector(textFieldTextChanged:) forControlEvents:UIControlEventEditingChanged];
    
    // 初始化时设置按钮状态
    [self updateForwardButtonState];
}

2. 实现按钮状态校验方法 #

创建单独方法统一处理按钮启用逻辑，同时去除输入内容两端空白字符，避免用户输入空格绕过校验：

- (void)updateForwardButtonState {
    NSString *trimmedLastName = [_lastName.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    NSString *trimmedFirstName = [_firstName.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    
    // 两个输入框都有非空内容时启用按钮
    _fwdButton.enabled = (trimmedLastName.length > 0 && trimmedFirstName.length > 0);
}

3. 简化textFieldDidBeginEditing方法 #

只保留必要的样式设置，移除错误的按钮判断逻辑：

-(void)textFieldDidBeginEditing:(UITextField *)textField {
    UIFont* boldFont = [UIFont fontWithName:@"Helvetica-Bold" size:24];
    
    [textField setFont:boldFont];
    textField.autocorrectionType = UITextAutocorrectionTypeNo;
    textField.autocapitalizationType = UITextAutocapitalizationTypeNone;
    
    // 若不需要开始编辑时清空内容，可移除以下行
    // textField.text = @"";
    
    if (textField == _lastName) {
        NSLog(@"user editing last...");
    } else {
        NSLog(@"user editing first");
    }
    
    // 开始编辑时更新按钮状态
    [self updateForwardButtonState];
}

4. 实现内容变化回调方法 #

- (void)textFieldTextChanged:(UITextField *)textField {
    [self updateForwardButtonState];
}

5. 修复Go按钮点击逻辑 #

即使按钮已做启用控制，仍需在点击方法中再次校验，彻底避免崩溃：

- (IBAction)forwardButtonTapped:(UIButton *)sender {
    NSString *trimmedLastName = [_lastName.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    NSString *trimmedFirstName = [_firstName.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    
    if (trimmedLastName.length == 0 || trimmedFirstName.length == 0) {
        UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"提示" message:@"No name - please reenter" preferredStyle:UIAlertControllerStyleAlert];
        [alert addAction:[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil]];
        [self presentViewController:alert animated:YES completion:nil];
        return;
    }
    
    // 执行原本的提交逻辑
}

内容的提问来源于stack exchange，提问作者user3741598