Best way to initite array of strings

[hyousef (Hasan Yousef)]

I know an empty array canbe initiated with one of the below, if there are others pls advice:

lines := []string{} 
// Or
lines := make([]string, 0)
// Or
var lines []string

What are the differences betwwen these methods, are they all equivalent, any special use for any of them?

[petrus]

CodeReviewComments

Declaring Empty Slices

When declaring an empty slice, prefer

var t []string

over

t := []string{}

The former declares a nil slice value, while the latter is non-nil but zero-length. They are functionally equivalent—their len and cap are both zero—but the nil slice is the preferred style.

Note that there are limited circumstances where a non-nil but zero-length slice is preferred, such as when encoding JSON objects (a nil slice encodes to null , while []string{} encodes to the JSON array [] ).

. . .

[ncw (Nick Craig-Wood)]

one

@hyousef

lines := string{}

This defines an empty slice lines

two

@hyousef

lines := make(string, 0)

The result of this should be the same as the above. Use the above unless you want to set the size or capacity to non-zero, eg

lines := make([]string, 5) // len(lines) == 5
lines := make([]string, 0, 5) // len(lines) == 0, cap(lines) = 5

The latter of these is useful for when appending to a slice.

three

@hyousef

var lines string

This makes a nil slice which isn’t quite the same thing as an empty slice. A nil slice is perfectly well behaved, has len(lines) == 0 and cap(lines) == 0. I would use this form if I was planning to append some (or no) items to it.

Interestingly when I compiled a simple function with each init method in, one and three produced identical code - basically zeroing the slice structure. two produced a lot more code, actually allocating stuff on the heap.

[hyousef (Hasan Yousef)]

Appreciate your detailed answer