Go Slices: `var s []int` or `s := make([]int, 0)` – Which Declaration is Best?

Declaring vs. Making Slices in Go: var s []int or s := make([]int, 0)?

In Go, slices are a powerful data structure that represent a flexible array-like type. When working with slices, you may have come across two different ways to declare them:

• Simple Declaration: var s []int
• make() Declaration: s := make([]int, 0)

Understanding the difference between these two approaches is crucial for writing efficient and idiomatic Go code.

var s []int

The simple declaration var s []int does not allocate any memory. It creates a nil slice, meaning that s points to an empty memory address. This declaration is typically used when you don't know the exact size of the slice you need upfront or when you need to allocate memory dynamically later on.

s := make([]int, 0)

In contrast, s := make([]int, 0) allocates memory for a slice with 0 elements. It is explicitly instructing the compiler to create a slice with a specific capacity, which is the maximum number of elements it can hold before it needs to grow. In this case, it has a capacity of 0. This approach is preferred when you know the exact size of the slice you need or when you want to avoid unnecessary memory reallocation.

Which One is Better?

In general, using var s []int is more idiomatic when you don't know the exact size of the slice you need or when you want to allocate memory dynamically. If you know the exact size upfront or need to avoid memory reallocation, s := make([]int, 0) is the better choice.

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