目标c – 目标c中的Swift全局变量和全局函数

发布时间：2020-12-16 03:07:33 所属栏目：百科来源：网络整理

导读：文件说： Global constants defined in C and Objective-C source files are automatically imported by the Swift compiler as Swift global constants. 但是,它并没有说出任何其他方式.我需要定义一个全局快捷常量,并且能够看到它像目标c一样像一个全局c常

文件说：

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

但是,它并没有说出任何其他方式.我需要定义一个全局快捷常量,并且能够看到它像目标c一样像一个全局c常量.喜欢在swift侧定义：

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

并且看到在客观c上使用它像

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

我该怎么办？我已经导入swift自动生成的标题,如：

#import "MyProject-Swift.h"

并且在Xcode中,如果我命令单击它,它需要我到正确的地方在swift代码,但在编译时我得到：

'User of undeclared Identifier CARDS'

在我的目标c方面.

解决方法

Here is the document关于它

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

全局变量(包括常量)从Objective-C无法访问.

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() {}
   class func cards() -> [String] { return CARDS }
}

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

（编辑：李大同）

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