文本框：shouldChangeCharactersInRange：replacementString： [英] textField:shouldChangeCharactersInRange:replacementString:

问题描述

如何更正此代码。我只想要数字和范围不应超过10.
我的代码是

How can I correct this code. I want only numbers and range should be not exceed to 10. My code is

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSUInteger newLength = [textField.text length] + [string length] - range.length;
    return (newLength > 10) ? NO : YES;

    static NSCharacterSet *charSet = nil;
    if(!charSet) {
        charSet = [[[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] invertedSet] retain];
    }
    NSRange location = [string rangeOfCharacterFromSet:charSet];
    return (location.location == NSNotFound);
}

推荐答案

这里的问题是什么在第一个返回之后没有执行。

The problem here is that anything after the first return is not executed.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSUInteger newLength = [textField.text length] + [string length] - range.length;
    return (newLength > 10) ? NO : YES;
    // unreachable!

所以你只是检查长度，而不是输入是否为数字。更改此行：

So you are just checking the length but not whether the input is numerical. Change this line:

return (newLength > 10) ? NO : YES;

这一个：

if (newLength > 10) return NO;

它应该有效。您也可以选择更改此项：

and it should work. You can also optionally change this:

[NSCharacterSet characterSetWithCharactersInString:@"0123456789"]

这个：

[NSCharacterSet decimalDigitCharacterSet]

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