目标c中的Swift全局函数和全局函数 [英] Swift globals and global functions in objective c

问题描述

$ b

在C语言和Objective-C源文件中定义的全局常量由Swift编译器自动导入，作为Swift全局常量。

但它没有提到任何其他方法。我需要定义一个全局快速常量，并且能够像全局常量一样看到它的一个目标c侧。像在快捷方面定义：

  public let CARDS = [card1，card2] 
 
 code> 

并且看到在目标c方面使用它像

  NSLog（@卡数：％d，[卡数]）
  



<我应该怎么做？我已经导入了swift自动生成的头文件，如：



  #importMyProject-Swift.h
  

并且在Xcode中如果我命令点击就可以了我在swift代码中的正确位置，但在编译时我得到：



 '未声明标识符卡的用户'
  

在我的客观c方面。


解决方案

以下是关于它的文档



您可以访问类或协议中的任何内容b $ b用@objc属性标记，只要它与
Objective-C兼容即可。这不包括Swift-only特性，例如这里列出的
：
$ b

• 泛型


• 元组
  
• 在Swift中定义的枚举


• 在Swift中定义的结构


• 在Swift中定义的顶级函数


• Swift中定义的全局变量
  
• Swift中定义的类型别
  
• Swift风格的变量


• 嵌套类型
  
• 咖喱函数
  
  

全局变量（包括常量）无法从Objective-C访问。

相反，您必须声明一个具有全局常量访问器的类。

  // Swift 
 public let CARDS = [card1，card2] 
 
 @objc class AppConstant {
 private init（）{} $ b $ class func cards（） - > [String] {return CARDS} 
} 
 
 // Objective-C 
 NSArray * cards = [AppConstant cards]; 
  

the documentation says:

Global constants defined in C and Objective-C source files are automatically imported by the Swift compiler as Swift global constants.

But it doesn't say anything about the other way around. I need to define a global swift constant and be able to see it one the objective c side like a global c constant. Like on the swift side define:

public let CARDS = ["card1", "card2"]

and see use it on the objective c side like

NSLog(@"Cards count: %d", [CARDS count])

What should I do? I've already imported the swift automatically generated header like:

#import "MyProject-Swift.h"

and in Xcode if I command-click on it, it takes me to the correct place in the swift code, but at compile time I get:

'User of undeclared Identifier CARDS'

on my objective c side.

解决方案

Here is the document about it

You’ll have access to anything within a class or protocol that’s marked with the @objc attribute as long as it’s compatible with Objective-C. This excludes Swift-only features such as those listed here:

• Generics
• Tuples
• Enumerations defined in Swift
• Structures defined in Swift
• Top-level functions defined in Swift
• Global variables defined in Swift
• Typealiases defined in Swift
• Swift-style variadics
• Nested types
• Curried functions

Global variables (including constants) are unaccessible from Objective-C.

Instead, you have to declare a class which has accessors for the global constants.

// Swift
public let CARDS = ["card1", "card2"]

@objc class AppConstant {
   private init() {}
   class func cards() -> [String] { return CARDS }
}

// Objective-C
NSArray *cards = [AppConstant cards];

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