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This article introduces the knowledge of "how to use blank identifiers in Go". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Like Python, the Go language has blank identifiers.

1. What is a blank identifier

A blank identifier is a placeholder for an unused value. It is represented by an underscore (_). Because blank identifiers do not have a name, they are also called anonymous placeholders.

In the Go language, it is not allowed to declare unused variables or import statements. That is, we cannot declare a variable and leave it unused. Similarly, if you import a package, you must also use it.

At this point, a blank identifier is needed.

two。 Unused assignment variable

If a function in Go returns multiple values, you must define an equal number of variables to hold those values. However, if you only need some of these values and no other values, if an assignment needs to match multiple left values, but one of the variables will not be used by the program, use a blank identifier instead. This variable avoids creating useless variables and clearly indicates that the value will be discarded.

As follows:

Result, error = Dosomething () if error {/ / handle error}

In the above code, result has nothing to do with the program, and subsequent code does not use it. If compiled, the Go compiler will report an error.

Result declared but not used

In this case, you can replace the result with an underscore or a blank identifier

As follows:

_, error = Dosomething () if error {/ / handle error}

Even if you declare a variable, you can ignore it later using a blank identifier, as shown in the following code:

Product, error = Dosomething () if error {/ / handle error} / / ignore unused variable_ = product

Use white space markers in for...range

Func Sum (numbers [] int) int {sum: = 0for _, number: = range numbers {sum + = number} return sum} 3. Unknown structure

You can use _ to distribute anything:

Var _ I = T {}

Cannot access this variable so that it will be optimized from the generated program. However, if the T type is not assigned to interface I, it may result in a compilation error. Therefore, in this case, it is used as a static assertion about the type.

4. Unused package

In Go, if you import a package, you must use it, or a compiler error will occur.

Imported and not used ""

A blank identifier can be used to resolve this compiler error.

There are two ways to use blank identifiers to resolve unused package errors, as follows:

The first: declare a global blank identifier (before the main () function) that has never been used in the package access symbol, such as Open in the following code:

Import "os" var _ = os.Openfunc main () {}

The second: add a blank identifier to the unused package

As follows:

Import _ "os" func main () {}

Blank identifiers make the code more readable by avoiding the use of unused variable declarations throughout the code.

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