xcode 如何使用 appendFormat 在 Swift 中格式化字符串？
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How to use appendFormat to format a string in Swift?
提问by kobuchi
I want to append a string to a NSMutableString using appendFormat, inserting white spaces to get a minimum length for my string.
我想使用 appendFormat 将字符串附加到 NSMutableString，插入空格以获得字符串的最小长度。
In objective-c, i just used
在objective-c中，我刚刚使用
[text.mutableString appendFormat:@"%-12s", "MyString"];
and I would get
我会得到
"MyString "
But in Swift, I tried
但在斯威夫特，我试过
text.mutableString.appendFormat("%-12s", "MyString")
and I get everything, but not "MyString ". It appears some random characters that I do not know where it came from.
我得到了一切，但不是“MyString”。出现一些随机字符，我不知道它来自哪里。
Is there anyone who knows why that happens, and what I should do?
有没有人知道为什么会发生这种情况，我应该怎么做？
Thank you guys!
谢谢你们！
采纳答案by Leo Dabus
You should use String's method stringByPaddingToLength()as follow:
您应该使用 String 的方法stringByPaddingToLength()如下：
let anyString = "MyString"
let padedString = anyString.stringByPaddingToLength(12, withString: " ", startingAtIndex: 0) // "MyString "
回答by Adam S
Through Ken's explanation that a Swift String object is notequivalent to the Objective-C C-style string (a null-terminated array of char) I found this answerwhich shows how to convert a Swift String object into a Cstring, which the %-12sformatting works correctly on.
通过 Ken 的解释，即 Swift String 对象不等同于 Objective-C C 样式字符串（以空结尾的数组char），我找到了这个答案，该答案显示了如何将 Swift String 对象转换为 Cstring，%-12s格式正确在。
You can use your existing formatting string as follows:
您可以使用现有的格式字符串，如下所示：
text.mutableString.appendFormat("%-12s", ("MyString" as NSString).UTF8String)
Some examples:
一些例子：
var str = "Test"
str += String(format:"%-12s", "Hello")
// "Test–y? " (Test, a dash, 11 random characters)
var str2 = "Test"
str2 += String(format:"%-12@", "Hello")
// "TestHello" (no padding)
var str3 = "Test"
str3 += String(format:"%-12s", ("Hello" as NSString).UTF8String)
// "TestHello " ('Hello' string is padded out to 12 chars)
回答by Ken Thomases
Try:
尝试：
text.mutableString.appendFormat("%-12@", "MyString")
In Swift, "MyString"is a Stringobject. The %sformat specifier causes appendFormat()to interpret its argument as a C-style string (a buffer of charterminated by a null char).
在 Swift 中，"MyString"是一个String对象。该%s格式说明使appendFormat()解释其作为C风格字符串参数（的缓冲器char以空终止char）。
In Objective-C, "MyString"is just such a C-style string. You would have to prefix it with an @to get an NSStringobject (@"MyString").
在Objective-C中，"MyString"就是这样一个C风格的字符串。您必须在它前面加上前缀@才能获得NSString对象 ( @"MyString")。
回答by muneeb
let space: Character = " "
text = "MyString" + String(count: 12, repeatedValue: space)
