When and Why Use Unnamed Arguments in Go?

Unnamed Arguments in Go

In Go, unnamed function arguments are valid and serve specific purposes. The language's parameter declaration syntax allows for optional parameter names:

ParameterDecl  = [ IdentifierList ] [ "..." ] Type .

This means that when calling a function, you are not required to specify the names of its parameters.

Reasons for Unnamed Arguments

• Unnecessary Reference: When a parameter is passed but not used within the function, naming it becomes redundant. Unnamed parameters indicate that the value is present but not referenced.
• Interface Implementation: To implement an interface with specific parameter signatures, you may need to declare unnamed parameters that are dictated by the interface.
• Discarding Values: If a function requires a parameter but you have no use for its value, you can create an unnamed parameter to satisfy the signature.
• Forward Compatibility: In libraries, unnamed parameters can be introduced in preparation for future enhancements, providing forward compatibility and avoiding breaking changes.

Example

Consider the moveLabel function from the andlabs/ui library:

func moveLabel(*Button) {
    ...
}

The unnamed *Button parameter indicates that a pointer to a Button is required, but the function does not refer to it by name. This allows the function to comply with a specific interface or function signature without the need for a named variable.

Limitations

You cannot mix named and unnamed parameters in a single function signature. If you specify a name for one parameter, all parameters must be named. You can use the blank identifier to indicate unused named parameters.

Related Questions

• Why must we declare a variable name when adding a method to a struct in Golang?
• Return map like 'ok' in Golang on normal functions
• Getting method parameter names in Golang

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