需要在iOS中将UITextField的字符输入限制为两个字符

我正在开发一个具有多个UITextFields的应用程序。对于一个UITextField，我已将其委托设置为self，并调用委托方法：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if([[string stringByTrimmingCharactersInSet:[NSCharacterSet controlCharacterSet]]
        isEqualToString:@""])
        return YES;

    NSString *previousValue = [[[textField.text stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]] stringByReplacingOccurrencesOfString:@"." withString:@""] stringByReplacingOccurrencesOfString:@"," withString:@""];
    string = [string stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]];
    NSString *modifiedValue = [NSString stringWithFormat:@"%@%@", previousValue, string];

    if ([modifiedValue length] == 1) {

        modifiedValue = [NSString stringWithFormat:@"0.0%@", string];

    }

    else if ([modifiedValue length] == 2) {

        modifiedValue = [NSString stringWithFormat:@"0.%@%@", previousValue, string];

    }

    else if ([modifiedValue length] > 2) {

        modifiedValue = [NSString stringWithFormat:@"%@.%@",[modifiedValue substringToIndex: modifiedValue.length-2],[modifiedValue substringFromIndex:modifiedValue.length-2]];

    }


    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    NSDecimalNumber *decimal = [NSDecimalNumber decimalNumberWithString:modifiedValue];
    modifiedValue = [formatter stringFromNumber:decimal];
    textField.text = modifiedValue;

    return NO;

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (textField == self.firstRestrictionTextField) {
// Do stuff you need in first textfield
}
if (textField == self.yourSecondTextField) {
// Do stuff for your second textfield
}

}

完成一项特定的任务。但是，我在同一屏幕上还有其他UITextFields，我想对其执行完全不同的操作，在本例中，将输入的字符数限制为仅两个。不幸的是，我在网上看到的唯一可行的方法是使用上述方法进行限制。如果我已经在使用上述方法为另一个UITextField执行完全不同的操作，那么这是否仍然可行？如果是，如何实现

作为记录，以下是我当前对委托方法的实现：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if([[string stringByTrimmingCharactersInSet:[NSCharacterSet controlCharacterSet]]
        isEqualToString:@""])
        return YES;

    NSString *previousValue = [[[textField.text stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]] stringByReplacingOccurrencesOfString:@"." withString:@""] stringByReplacingOccurrencesOfString:@"," withString:@""];
    string = [string stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]];
    NSString *modifiedValue = [NSString stringWithFormat:@"%@%@", previousValue, string];

    if ([modifiedValue length] == 1) {

        modifiedValue = [NSString stringWithFormat:@"0.0%@", string];

    }

    else if ([modifiedValue length] == 2) {

        modifiedValue = [NSString stringWithFormat:@"0.%@%@", previousValue, string];

    }

    else if ([modifiedValue length] > 2) {

        modifiedValue = [NSString stringWithFormat:@"%@.%@",[modifiedValue substringToIndex: modifiedValue.length-2],[modifiedValue substringFromIndex:modifiedValue.length-2]];

    }


    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    NSDecimalNumber *decimal = [NSDecimalNumber decimalNumberWithString:modifiedValue];
    modifiedValue = [formatter stringFromNumber:decimal];
    textField.text = modifiedValue;

    return NO;

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (textField == self.firstRestrictionTextField) {
// Do stuff you need in first textfield
}
if (textField == self.yourSecondTextField) {
// Do stuff for your second textfield
}

}

---

您希望使用相同的方法。见第一部分：

-（BOOL）textField:（UITextField*）textField

该方法允许您标识触发此委托方法的文本字段。然后，您只需要做一些逻辑来为不同的文本字段执行不同的任务

比如：

---

您可以为每个UITextField设置不同的标记，并获取特定UITextField的textField.tag，以定义委托方法中的行为

在类中创建一个

UITextField

属性：

@interface MyObject ()
@property (nonatomic, retain) UITextField *textField1;
@end

self.firstRestrictionTextField.delegate = self;
self.yourSecondTextField.delegate = self;

然后在委托方法中，只需检查文本字段是否与您保存的文本字段相同：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    . . .

    if (textField == [self textField1]) {
        // do stuff here
    } else {
        // do stuff here for other text fields
    }

    . . .
}

---

将两个文本字段都用作类中的属性。例如，假设这是控制器的接口

@interface YourViewController : UIViewContoller <UITextFieldDelegate> {
}

/*
* other properties
*/
@property(nonatomic, retain) UITextField *firstRestrictionTextField;
@property(nonatomic, retain) UITextField *yourSecondTextField;

@end

当您实现委托方法时：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if([[string stringByTrimmingCharactersInSet:[NSCharacterSet controlCharacterSet]]
        isEqualToString:@""])
        return YES;

    NSString *previousValue = [[[textField.text stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]] stringByReplacingOccurrencesOfString:@"." withString:@""] stringByReplacingOccurrencesOfString:@"," withString:@""];
    string = [string stringByTrimmingCharactersInSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]];
    NSString *modifiedValue = [NSString stringWithFormat:@"%@%@", previousValue, string];

    if ([modifiedValue length] == 1) {

        modifiedValue = [NSString stringWithFormat:@"0.0%@", string];

    }

    else if ([modifiedValue length] == 2) {

        modifiedValue = [NSString stringWithFormat:@"0.%@%@", previousValue, string];

    }

    else if ([modifiedValue length] > 2) {

        modifiedValue = [NSString stringWithFormat:@"%@.%@",[modifiedValue substringToIndex: modifiedValue.length-2],[modifiedValue substringFromIndex:modifiedValue.length-2]];

    }


    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    NSDecimalNumber *decimal = [NSDecimalNumber decimalNumberWithString:modifiedValue];
    modifiedValue = [formatter stringFromNumber:decimal];
    textField.text = modifiedValue;

    return NO;

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (textField == self.firstRestrictionTextField) {
// Do stuff you need in first textfield
}
if (textField == self.yourSecondTextField) {
// Do stuff for your second textfield
}

}

声明一个文本字段：

    @property(nonatomic, strong)UITextField *textField1;
    @property(nonatomic, strong)UITextField *textField2;
    //etc

给它一个标签：

self.textField1.tag = 1;//or whatever
self.textField2.tag = 2;//or whatever
//etc

然后在

textField:shouldChangeCharactersRange:

中，您可以进行不同的测试和行为：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

if(textField.tag == 1){
//textfield1
}
//etc
}

---

非常感谢您的解决方案。您的答案是最完整的：-）由于委托方法将实际的UITextField输入作为参数，因此不需要使用标记（在我看来，标记有点冒险，因为它们本质上是全局变量）。