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控制TextField的内容长度

参考如下代码(下例是控制设置交易密码,控制6位):

- (void)viewWillAppear:(BOOL)animated{    [super viewWillAppear:animated];        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldDidChange:) name:UITextFieldTextDidChangeNotification object:nil];}- (void)viewDidDisappear:(BOOL)animated{    [super viewDidDisappear:animated];    [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:nil];}- (void)textFieldDidChange:(NSNotification *)notification{    UITextField *textField = (UITextField *)notification.object;        if ( textField.text.length > 6 && textField == _oldTransactionPasswordTextField)    {        _oldTransactionPasswordTextField.text = [textField.text substringToIndex:6];    }        if ( textField.text.length > 6 && textField == _transPasswordTextField)    {        _transPasswordTextField.text = [textField.text substringToIndex:6];    }}

采用通知做法比delegate中

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string这个方法要好一些(个人觉得)

 

控制TextField的内容长度