Swift +宏参数 [英] Swift + macro parameters

问题描述

我在 Swift 中阅读了所有与Macros相关的问答，而且我确实发现 Swift中的所有东西现在都是全球的， 我是对的吗？

I read all Q&A related to Macros in Swift, And i did figure out that everything in Swift now global, Am i right?

我的实际问题是，如果我有一个宏我在其中需要参数传递然后如何在 Swift 语言中传递它？

And my actual question is that if i have a macro in which i need parameters to be pass then how can i pass it in Swift language?

例如

Objective-C Macro

#define COLOR_CODE（红色，绿色，蓝色） ，alpha）[UIColor colorWithRed：红色/ 255.0绿色：绿色/ 255.0蓝色：蓝色/ 255.0 alpha：alpha]

什么是 Swift 上面宏的语法？

推荐答案

正如0O0O0O0所述，宏在感觉编译器应该看到 COLOR_CODE（0,0,0,1）并将其替换为 [UIColor colorWithRed：0 / 255.0 green：0 /255.0蓝色：0 / 255.0 alpha：1] 在Swift中不存在。

As 0O0O0O0 mentioned, macros in the sense of "The compiler should see COLOR_CODE(0, 0, 0, 1) and replace it with [UIColor colorWithRed: 0/255.0 green: 0/255.0 blue: 0/255.0 alpha: 1]" do not exist in Swift.

C中的宏可以用于生成的方式令人困惑的错误或消息：

Macros in C can be used in ways that produce confusing error messages:

#define IS_EQUAL_TO_ME(argument) [self isEqual: argument]

BOOL func(id argument) {
    return IS_EQUAL_TO_ME(argument);
}

// Error: Use of undeclared identifier 'self'

或破坏可读性：

#define OPEN_BLOCK {
#define CLOSE_WITH_EXIT_IF_FALSE } else { exit (0); }

if (x < 0)
OPEN_BLOCK
    return 10;
CLOSE_WITH_EXIT_IF_FALSE

对于像 COLOR_CODE C的一个常用推荐策略是使用内联函数：

For simple cases like COLOR_CODE a commonly recommended strategy for C was to use inline functions:

NS_INLINE UIColor *ColorCode(CGFloat r, CGFloat g, CGFloat b, CGFloat a) {
    return [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:a];
}

这与宏具有相同的性能，因为它会被内联到相同的代码，但强类型，不依赖于宏处理规则。此代码也直接转换为Swift：

This had the same performance as the macro in that it would get inlined to the same code but is strongly typed and does not depend on macro processing rules. This code also has a direct translation to Swift:

func ColorCode(red:CGFloat, green:CGFloat, blue:CGFloat, alpha:CGFloat) -> UIColor {
    return UIColor(red: red/255, green: green/255, blue: blue/255, alpha: alpha)
}

因为一切都是全局的，你可以在任何文件中声明它并在同一模块中的任何其他文件中使用它。在这种情况下，由编译器决定是否内联函数。

Because "everything is global" you can declare this in any file and use it in any other file in the same module. It is up to the compiler in this case to decide whether or not to inline the function.

这篇关于Swift +宏参数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！