限制小数点到需要的 [英] Limiting decimal points to what is needed

问题描述

可能重复：

舍入数字

目标-C：如何在float中截断额外的零？

更正浮点数

在Objective C中，我有一个双倍的数字，得到如下计算的答案：

In Objective C, I have a double which receives the answer to a calculation as shown:

double answer = a / b;

双变量有时可以是一个整数，但也可以是一个例子，例如

The double variable can sometimes be a whole integer but can also be a fraction e.g.

NSLog(@"%f", answer)

这可以返回2.000000或5.142394或2.142000。

This can return 2.000000 or 5.142394 or 2.142000.

我想知道是否有方法来编辑小数位，使尾随0的是不可见的例如：

I was wondering if there was a way to edit the decimal places so that the trailing 0's are not visible for example:

2.000000将是2

5.142394将是5.142394

2.142000将是2.142

2.000000 would be 2
5.142394 would be 5.142394
2.142000 would be 2.142

如何做？

推荐答案

如果你愿意要硬编码你以后的小数位数，这将给你两位小数：

If you'd like to hard-code the number of decimal places you're after, this would give you two decimal places:

NSLog(@"%.2f", answer);

详细了解格式说明符：

http://www.cplusplus.com/reference/clibrary/cstdio/printf/

或者，如果您想要即时更改小数位数，请考虑使用 NSNumberFormatter 类：

Alternatively, if you'd like to change the number of decimal places on-the-fly, consider using the NSNumberFormatter class:

int maxDigitsAfterDecimal = 3; // here's where you set the dp

NSNumberFormatter * nf = [[NSNumberFormatter alloc] init];
[nf setMaximumFractionDigits:maxDigitsAfterDecimal];

NSString * trimmed = [nf stringFromNumber:[NSNumber numberWithDouble:3.14159]];
NSLog(@"%@", trimmed); // in this case, 3.142

[nf release];

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