英文:
Why would we use blank identifiers in Go?
问题
我发现对于空白标识符的使用有点难以理解。我已经查看了《Effective Go》，并理解了他们描述的大多数用例，但是在查看教程时，我在一个路由处理函数中遇到了以下代码：
var person Person
_ = json.NewDecoder(req.Body).Decode(&person)
在第一行中，我们创建了一个类型为Person的新空变量（之前定义的结构体），然后我假设：
&person是将person变量通过引用传递，- 以便由
Decode函数填充数据。
然后，该函数继续执行一些其他任务，然后对数据进行编码并返回JSON响应。
为什么我们需要将解码赋值给一个空白标识符？我们不能只运行json.NewDecoder(req.Body).Decode(&person)吗？如果不能，为什么？
英文:
I'm finding the use of the blank identifier a little hard to understand. I've looked at effective go and understand most of the use cases they describe but then looking at a tutorial I came across this in a route handler function:
var person Person
_ = json.NewDecoder(req.Body).Decode(&person)
in the first line we create a new empty variable of type Person (a struct previously defined) and then I assume that
&personis passing the person var in by reference,- to be filled with data by the
Decodefunction
this function then goes on to perform a few more tasks before encoding and returning a json response.
Why do we need have the decode assigned to a blank identifier? Couldn't we just run json.NewDecoder(req.Body).Decode(&person) ? if we can't, why not?
答案1
得分: 1
我假设你正在学习Go语言，并且询问是因为你无法理解为什么这个例子使用了这种做法。
正如@JimB在评论中提到的，这个例子的作者并不需要这样做，他们只是忽略了错误返回。
英文:
I'm assuming you're learning golang and asking because you can't identify why this example used this practice.
As @JimB mentioned in comments, the example writer didn't need to do this they're simply ignoring the Error return.
答案2
得分: 1
空白标识符_也可以用于严格地在结构体中提供键。参考这个链接。
不强制指定键：
type SomeStruct struct {
FirstField string
SecondField bool
}
myStruct := SomeStruct{"", false}
强制指定键值（消除对值排序的依赖）：
type SomeStruct struct {
FirstField string
SecondField bool
_ struct{}
}
// 编译错误
myStruct := SomeStruct{"", false}
上述代码将报错SomeStruct字面量中的值过少。
英文:
The blank identifier _ can be used to strictly provide the keys in a struct too. See this for reference
Without enforcing
type SomeStruct struct {
FirstField string
SecondField bool
}
myStruct := SomeStruct{"", false}
Enforcing to mention the key for the value (Removes the dependency of ordering the values)
type SomeSturct struct {
FirstField string
SecondField bool
_ struct{}
}
// COMPILATION ERROR
myStruct := SomeSturct{"", false}
The above will give the error too few values in SomeSturct literal
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