英文:
Conditionally Define a Variable
问题
在JavaScript中，我们可以这样做：
var x = expr1 || expr2;
如果expr1不是undefined，它将被复制到x，如果它是undefined，则expr2将被复制到x。在Go语言中，我们可以使用以下方式：
var x string
if expr1 == "" {
x = expr1
} else {
x = expr2
}
是否有一种简写形式来实现这个功能？如果没有，为什么呢？
英文:
In javascript we can do this:
var x string = expr1 || expr2
If expr1 is not undefined, it will be copied to x, if it is undefined, expr2 will be copied to x. In go, we can use:
if expr1 == "" { var string x = expr1 } else { var string x = expr2 }
Is there are shorthand for this? If not, why?
答案1
得分: 4
我不知道关于“为什么”的原因，但你可以始终使用以下代码：
var a []string = expr1
if a == nil {
a = expr2
}
英文:
I don't know about the "why" however you can always use this :
var a []string = expr1
if a == nil {
a = expr2
}
答案2
得分: 4
《Go编程语言规范》
声明和作用域
声明将非空白标识符绑定到常量、类型、变量、函数、标签或包。程序中的每个标识符都必须声明。
零值
当通过声明或调用make或new来分配内存以存储一个值时，并且没有提供显式初始化，内存将被赋予默认初始化。这样的值的每个元素都被设置为其类型的零值：布尔类型为false，整数类型为0，浮点数类型为0.0，字符串类型为""，指针、函数、接口、切片、通道和映射类型为nil。
类型系统
静态类型检查
动态类型检查
英文:
> The Go Programming Language Specification
>
> Declarations and scope
>
> A declaration binds a non-blank identifier to a constant, type,
> variable, function, label, or package. Every identifier in a program
> must be declared.
>
> The zero value
>
> When memory is allocated to store a value, either through a
> declaration or a call of make or new, and no explicit initialization
> is provided, the memory is given a default initialization. Each
> element of such a value is set to the zero value for its type: false
> for booleans, 0 for integers, 0.0 for floats, "" for strings, and nil
> for pointers, functions, interfaces, slices, channels, and maps.
> Type system
>
> Static type-checking
>
> Dynamic type-checking
Go is a statically typed language. All variables must be declared at compile time and they have an well-defined initial value. JavaScript is a dynamically typed language. Variables are declared at run time. Therefore, the JavaScript construct makes no sense in Go.
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