xcode 如何快速舍入 NSDecimalNumber？
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How to round an NSDecimalNumber in swift?
提问by Naldhelaan
I can't find any resources on this, and I've been trying all sorts of stuff, but nothing works.
我找不到这方面的任何资源，我一直在尝试各种东西，但没有任何效果。
According to Apple's documentation, you round an NSDecimalNumber like this:
根据 Apple 的文档，您可以像这样对 NSDecimalNumber 进行四舍五入：
NSDecimalNumber.decimalNumberByRoundingAccordingToBehavior(<#behavior: NSDecimalNumberBehaviors?#>)
It takes in an NSDecimalNumberBehavior, which I'm unsure how to manipulate since it (1) cannot be initiated into a variable and have it's properties changed, and (2) the roundingMode() method according to the documentation doesn't take any parameters, but Xcode fills in a parameter space for "self".
它接受一个 NSDecimalNumberBehavior，我不确定如何操作它，因为它 (1) 无法初始化为变量并更改其属性，并且 (2) 根据文档的 roundingMode() 方法不接受任何参数，但 Xcode 为“self”填充了一个参数空间。
I'm totally lost on this. Back to the basic question; How can I round an NSDecimalNumber in swift?
我完全迷失了这一点。回到基本问题；如何快速舍入 NSDecimalNumber？
Thanks in advance
提前致谢
采纳答案by ?zgür Ersil
you can do it like that
你可以这样做
let x = 5
let y = 2
let total = x.decimalNumberByDividingBy(y).decimalNumberByRoundingAccordingToBehavior( NSDecimalNumberHandler(roundingMode: NSRoundingMode.RoundUp, scale: 0, raiseOnExactness: false, raiseOnOverflow: false, raiseOnUnderflow: false, raiseOnDivideByZero: false))
回答by Arkku
NSDecimalNumberBehaviorsis a protocoland thus cannot be instantiated. You need an object of a classconforming to the protocol. Apple provides the class NSDecimalNumberHandlerfor this purpose, e.g.:
NSDecimalNumberBehaviors是一个协议，因此不能被实例化。您需要一个符合协议的类的对象。AppleNSDecimalNumberHandler为此目的提供了该类，例如：
let handler = NSDecimalNumberHandler(roundingMode: NSRoundingMode.RoundBankers, scale: 0, raiseOnExactness: false, raiseOnOverflow: false, raiseOnUnderflow: false, raiseOnDivideByZero: false)
let rounded = dec.decimalNumberByRoundingAccordingToBehavior(handler)
The scaleargument is the number of decimals you want, i.e., 0rounds to an integer.
该scale参数是要小数，即数量0回合的整数。
回答by smileBot
// get a decimal num from a string
let num = NSDecimalNumber.init(string: numStr)
// create an NSDecimalNumberHandler instance
let behaviour = NSDecimalNumberHandler(roundingMode:.RoundUp,
scale: 1, raiseOnExactness: false,
raiseOnOverflow: false, raiseOnUnderflow:
false, raiseOnDivideByZero: false)
// pass the handler to the method decimalNumberByRoundingAccordingToBehaviour.
// This is an instance method on NSDecimalNumber that takes an object that
// conforms to the protocol NSDecimalNumberBehaviors, which NSDecimalNumberHandler does!
let numRounded = num.decimalNumberByRoundingAccordingToBehavior(behaviour)
