swiftui double with 7 decimals without rounding

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英文:

swiftui double with 7 decimals without rounding

问题

我在SwuifUI中有一个带有7位小数的数字

```swift
@State var newLatitude : Double = 47.6364658

Text("\(newLatitude)") //这会显示47.636466

但是它会自动四舍五入为只有6位小数的47.636466

我该如何避免这种情况?
使用另一种数据类型吗?我仍然想使用Double,因为我有一个共享的Kotlin仓库。

而且我需要确切的7位小数,不要四舍五入,因为这是一个地理位置点。

我从Kotlin共享仓库获取数据的方式:

func getDoubleFromKotlin() {
    Task{
        do{
            try await repo.getData().watch(block:{myValue in                           
                self.newLatitude = myValue.latitude as Double//应该使用什么数据类型?                              
            })
        }
    }
}

newLatitude 应该使用什么数据类型,才不会被自动四舍五入并且保留真实的7位小数值?


<details>
<summary>英文:</summary>

I have a number with 7 decimals in SwuifUI:
```swift
@State var newLatitude : Double = 47.6364658

Text(&quot;\(newLatitude)&quot;) //this displays 47.636466

But this will round automatically to 47.636466 that only has 6 decimals

How can I avoid this?
Use another data type? I still want to use the Double because I have a shared Kotlin repo.

Also I need the exact 7 decimals without rounding because this is a geolocation point.

The way that i get the data from kotlin shared repo:

func getDoubleFromKotlin() {
    Task{
        do{
            try await repo.getData().watch(block:{myValue in                           
                self.newLatitude = myValue.latitude as Double// what data type should be?                             
            })
        }
    }
}

What type new latitude should have to not be automatically rounded and lose the real 7 decimal value?

答案1

得分: 3

为了回答原始问题,你只需正确格式化你的数值。在SwiftUI中,你可以直接在TextField中这样做:

Text(newLatitude.formatted(.number.precision(.fractionLength(2...))))

开放范围,2...,意味着它将使用至少2位小数数字,最多与数值包含的位数一样多。

这适用于Double,但你也可以使用Decimal

英文:

To answer the original question, all you need to do is to properly format your value. In SwiftUI you can do it directly in the TextField

Text(newLatitude.formatted(.number.precision(.fractionLength(2...))))

The open ended range, 2..., will mean it will use at least 2 decimal digits and up to as many as the value contains.

This works fine with Double but you can also use Decimal

答案2

得分: 1

我建议使用Decimal128,这是Realm在SwiftKotlin中都支持的数据类型。

它非常强大 - 甚至可以存储和处理货币;它类似于NSDecimalNumber。以下是一些Swift示例:

var decNum = Decimal128(value: 47.6364658) // 将decimal转换为Decimal128

var stringNum = Decimal128(string: "47.6364658") // 将字符串转换为Decimal128

var intNum = Decimal128(integerLiteral: 44) // 将整数转换为Decimal128

甚至可以从NSNumber中创建:

let num = NSDecimalNumber(decimal: 47.6364658)
var x = Decimal128(number: num)

您还可以轻松获取其数量级,这在计算距离时很方便:

let m = num.magnitude

将其作为字符串以输出到UI:

let s = dec128Num.stringValue
print(s)

47.6364658

如果需要在Swift中格式化数字,请使用NSNumberFormatter,它提供了许多关于有效数字等方面的灵活性。我不清楚Kotlin中的等效方法是什么。

英文:

I would suggest using Decimal128, which is a Realm supported type in both Swift as well as Kotlin.

It's quite powerful - you can even store and work with currency; it's similar to NSDecimalNumber. Here's some Swift examples:

var decNum = Decimal128(value: 47.6364658) //decimal to Decimal128

var stringNum = Decimal128(string: &quot;47.6364658&quot;) //string to Decimal128

var intNum = Decimal128(integerLiteral: 44) //int to Decimal128

or even from an NSNumber

let num = NSDecimalNumber(decimal: 47.6364658)
var x = Decimal128(number: num)

You can also easily get the magnitude, which is handy when calculating distances

let m = num.magnitude

Get it as a string for outputting to UI

let s = dec128Num.stringValue
print(s)

47.6364658

If you need to format the number in Swift, please use NSNumberFormatter which provides a lot of flexibility for significant digits etc. I don't know what the Kotlin equivalent is.

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  • 本文由 发表于 2023年3月4日 05:24:02
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