为打印而填充一个快速的字符串。

I'm trying to print a list of Strings all padded to the same width.

我正在打印一个字符串列表，所有的字符串都被填充到相同的宽度。

In C, I would use something like printf("%40s", cstr), where cstr is a C string.

在C中，我将使用printf(“%40”，cstr)，其中cstr是一个C字符串。

In Swift, the best I could come up is this:

在斯威夫特的书中，我能想到的最好的一句话是:

line += String(format: "%40s",string.cStringUsingEncoding(<someEncoding>))

Is there a better way ?

有更好的办法吗?

3 个解决方案

#1

NSString has the stringByPaddingToLength: method:

NSString有stringByPaddingToLength:方法:

line += string.stringByPaddingToLength(40, withString: " ", startingAtIndex: 0)

#2

In Swift 3 you can use:

在Swift 3中，您可以使用:

let str = "Test string"
let paddedStr = str.padding(toLength: 20, withPad: " ", startingAt: 0)

Result string: "Test string "

结果字符串:“测试字符串”

If you need to pad to the left the text (right justify), you can write the following function as an extension to String:

如果你需要把文本(右对齐)移到左边，你可以把下面的函数作为字符串的扩展:

extension String {
    func leftPadding(toLength: Int, withPad character: Character) -> String {
        let newLength = self.characters.count
        if newLength < toLength {
            return String(repeatElement(character, count: toLength - newLength)) + self
        } else {
            return self.substring(from: index(self.startIndex, offsetBy: newLength - toLength))
        }
    }
}

So if you write:

所以,如果你写:

let str = "Test string"
let paddedStr = str.leftPadding(toLength: 20, withPad: " ")

Result string: " Test string"

结果字符串:“测试字符串”

In Swift 4 the substring method is deprecated and there are a number of new methods to obtain a substring. Either prefix, suffix or subscripting the String with a Range<String.Index>.

在Swift 4中，不赞成使用子字符串方法，并且有许多新方法来获取子字符串。带范围 的前缀、后缀或下标。

For the previous extension we can use the suffix method to accomplish the same result. Since the suffix method returns a String.SubSequence, it needs to be converted into a String before being returned.

对于前面的扩展，我们可以使用后缀方法来完成相同的结果。因为后缀方法返回一个字符串。在返回之前，需要将其转换为字符串。

extension String {
    func leftPadding(toLength: Int, withPad character: Character) -> String {
        let stringLength = self.characters.count
        if stringLength < toLength {
            return String(repeatElement(character, count: toLength - stringLength)) + self
        } else {
            return String(self.suffix(toLength))
        }
    }
}

#3

Put all string-format-code into extension and reuse it wherever you want.

将所有字符串格式代码放到扩展中，并在任何需要的地方重用它。

extension String {
    func padding(length: Int) -> String {
        return self.stringByPaddingToLength(length, withString: " ", startingAtIndex: 0)
    }

    func padding(length: Int, paddingString: String) -> String {
        return self.stringByPaddingToLength(length, withString: paddingString, startingAtIndex: 0)
    }
}

var str = "str"
print(str.padding(10)) // "str       "
print(str.padding(10, paddingString: "+")) // "str+++++++"