What are the Different Ways to Define an Empty Slice in Go, and When Should I Use Each?

How to Define an Empty Slice in Go

In Go, an empty slice can be defined in several ways, leaving some programmers wondering about the differences or advantages of each approach.

Three Common Methods

1. var foo []int: This simply initializes the variable foo as a slice of integers with its initial value set to nil.
2. foo := []int{}: This is a short variable declaration that initializes foo as an empty slice of integers. The braces {} indicate that this is an empty slice.
3. foo := make([]int, 0): The make function can be used to explicitly create an empty slice of a specified type and capacity. In this case, 0 is used as the capacity.

Differences

The main difference between these three methods is that (1) initializes foo to nil while (2) and (3) assign non-nil empty slices to foo.

Commonalities

Regardless of the method used, all three results share the following attributes:

• Slice length is zero (len(foo) == 0)
• Slice capacity is zero (cap(foo) == 0)
• No memory is allocated during these initializations

Best Approach

The choice of which method to use depends on the specific use case.

• For nil slices that will be reassigned later, var foo []int is suitable.
• For short variable declarations, foo := []int{} or foo := make([]int, 0) can be concise options.
• For variable declarations with explicit initializers, var foo = []int{} or var foo = make([]int, 0) provide clear and readable intentions.

Summary

All three methods are valid for defining an empty slice in Go, with (1) being used for nil slices and (2) and (3) being interchangeable for non-nil empty slices. The appropriate choice depends on the specific context and preferences of the developer.

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