What is the Purpose of the Underscore Comma ('_') in Go Declarations?

The Mysterious "_," in Go Declarations: A Beginner's Guide

In the realm of Go programming, the peculiar "_," (underscore comma) often sparks confusion among aspiring Go programmers. Let's dive into what it represents and why it's employed in certain scenarios.

Understanding the "_," (Underscore Comma)

The "_," is known as the "blank identifier" or "discard variable." In a variable declaration, it serves as a placeholder to discard a returned value that you're not interested in. For example:

_, prs := m["example"]

In this declaration, the variable prs is assigned the value from the map m associated with the key "example." However, the first return value, typically an error or a flag indicating success, is ignored using the blank identifier.

Why Use the Blank Identifier?

The blank identifier is primarily used to avoid declaring unnecessary variables. Go's strict typing system forbids declaring variables without assigning them a value. By employing the blank identifier, you're essentially telling the compiler that you're aware of the return value's existence but have no need for it.

This technique is particularly beneficial when working with functions that return multiple values, one of which you're not interested in. For instance, consider coord(p), which returns three values: x, y, and z. If you're only interested in the y value, you can use the blank identifier to discard the other two:

_, y, _ := coord(p)

Other Uses of the Blank Identifier

Apart from variable declarations, the blank identifier has another use case: importing packages without assigning them to an identifier. This is useful when you want to access package-level functions or constants without using a prefixed package name.

Conclusion

The blank identifier ("_,") in Go declarations serves two main purposes: ignoring return values in variable declarations and importing packages without an assigned identifier. By understanding its functionality, you'll be equipped to effectively handle multiple return values and keep your Go code concise and efficient.

The above is the detailed content of What is the Purpose of the Underscore Comma ('_') in Go Declarations?. For more information, please follow other related articles on the PHP Chinese website!