找出字符串是否为数字 [英] Finding out whether a string is numeric or not

问题描述

我们如何检查字符串是否仅由数字组成。我从字符串中取出一个子字符串，并想检查它是否是一个数字子字符串。

How can we check if a string is made up of numbers only. I am taking out a substring from a string and want to check if it is a numeric substring or not.

NSString *newString = [myString substringWithRange:NSMakeRange(2,3)];

推荐答案

这是一种不依赖有限的方式尝试将字符串解析为数字的精度：

Here's one way that doesn't rely on the limited precision of attempting to parse the string as a number:

NSCharacterSet* notDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
if ([newString rangeOfCharacterFromSet:notDigits].location == NSNotFound)
{
    // newString consists only of the digits 0 through 9
}

参见 + [NSCharacterSet decimalDigitCharacterSet] 和 - [NSString rangeOfCharacterFromSet：] 。

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