限制一倍到两位小数[重复]

How do I achieve the following conversion from double to a string:

如何实现从double到字符串的以下转换:

1.4324 => "1.43"
9.4000 => "9.4"
43.000 => "43"

i.e. I want to round to to decimal places but dont want any trailing zeros, ie i dont want

也就是说，我想四舍五入到小数点后几位，但是我不想要后面的零

9.4 => "9.40" (wrong)
43.000 => "43.00" (wrong)

So this code which I have now doesn't work as it displays excess zeros:

所以我现在的代码不起作用因为它显示了多余的0:

[NSString stringWithFormat: @"%.2f", total]

5 个解决方案

#1

Use NSNumberFormatter. See the Data Formatting Programming Guide's chapter on Number Formatters.

使用NSNumberFormatter。参见数据格式编程指南关于数字格式器的章节。

#2

You made simple mistake. This will work:

你犯简单的错误。这将工作:

[NSString stringWithFormat: @"%.2lf", total]

#3

The easiest way is to probably roll your own. I've had to do this in C before since there's no way to get the behavior you want with printf formatting.

最简单的方法可能是自己卷。我之前在C语言中也做过，因为无法获得printf格式所需的行为。

It doesn't appear to be much easier in Objective-C either. I'd give this a try:

在Objective-C中看起来也没那么简单。我想尝试一下:

NSString *ftotal = [NSString stringWithFormat: @"%.2f", total];
while ([ftotal hasSuffix:@"0"]) {
    ftotal = [ftotal subStringToIndex [ftotal length]-1];
}
if ([ftotal hasSuffix:@"."]) {
    ftotal = [ftotal subStringToIndex [ftotal length]-1];
}

or this (possibly faster) variant:

或者这个(可能更快)的变体:

NSString *ftotal = [NSString stringWithFormat: @"%.2f", total];
if ([ftotal hasSuffix:@".00"]) {
    ftotal = [ftotal subStringToIndex [ftotal length]-3];
} else {
    if ([ftotal hasSuffix:@"0"]) {
        ftotal = [ftotal subStringToIndex [ftotal length]-1];
    }
}

The stringWithFormat guarantees there will always be a ".nn" at the end (where n is a digit character). The while and if simply strip off trailing zeros and the trailing decimal if it was an integer.

stringWithFormat保证始终存在一个"。最后(n是一个数字字符)。如果是整数，则去掉末尾的0和末尾的小数。

Obviously, you may want to put it in a function or class so you can get at it from anywhere without having to duplicate the code all over the place.

显然，您可能想把它放在一个函数或类中，这样您就可以从任何地方得到它，而不必在整个地方复制代码。

#4

I'm not familiar with objective C, but this isn't possible with standard printf-style formatting.

我不熟悉objective - C，但是使用标准的printf样式格式是不可能的。

Using %g would sort-of work, but for large or small numbers it would use scientific notation (eg 9.6e+6, 4.2e-7) rather than decimal notation.

使用%g将是一种工作，但是对于大或小的数字，它将使用科学的表示法(如9.6e+6, 4.2e-7)而不是十进制表示法。

The equivalent question was asked for C/C++ here, and in that case the answer is to use %f and then strip any trailing 0's from the string. Not exactly elegant.

在这里，等效的问题被要求使用C/ c++，在这种情况下，答案是使用%f，然后从字符串中去掉任何尾随0。不是优雅。

#5

-2

I am pretty sure that [[NSNumber numberWithFloat:f] stringValue] does exactly what you want.

我很确定[NSNumber numberWithFloat:f] stringValue]正是你想要的。

#1