使用可变参数格式化字符串 [英] Format string with variadic arguments

问题描述

我有String扩展名

I have extension for String

func localized(table: String? = nil, bundle: Bundle = .main, args: CVarArg...) -> String {
  return String(
    format: NSLocalizedString(
      self,
      tableName: table,
      bundle: bundle,
      value: self,
      comment: ""
    ),
    args
  )
}

Localizable.strings文件:

Localizable.strings file:

"%d seconds ago" = "%d seconds ago";

用法:

print("%d seconds ago".localized(args: 5))
print(String.localizedStringWithFormat("%d seconds ago", 5))

结果:

<some_random_number_here> seconds ago.
5 seconds ago.

有人可以向我解释我该怎么做吗?

Can someone explain me what do I do wrong?

推荐答案

String具有两个类似的初始化程序:

String has two similar initializers:

init(format: String, _ arguments: CVarArg...)
init(format: String, arguments: [CVarArg])

第一个使用不同数量的参数，第二个使用 具有所有参数的数组:

The first one takes a varying number of arguments, the second one an array with all arguments:

print(String(format: "x=%d, y=%d", 1, 2))
print(String(format: "x=%d, y=%d", arguments: [1, 2]))

在您的localized方法中，args: CVarArg...是可变参数 并且这些在函数体内以 array 的形式提供 的类型，在这种情况下为[CVarArg]. 因此，必须将其传递给String(format: arguments:):

In your localized method, args: CVarArg... is a variadic parameter and those are made available within the functions body as an array of the appropriated type, in this case [CVarArg]. Therefore it must be passed to String(format: arguments:):

func localized(table: String? = nil, bundle: Bundle = .main, args: CVarArg...) -> String {
  return String(
    format: NSLocalizedString(
      self,
      tableName: table,
      bundle: bundle,
      value: self,
      comment: ""
    ),
    arguments: args   // <--- HERE
  )
}

另请参见函数中的"可变参数"" 快速参考.

这篇关于使用可变参数格式化字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！