Go language slice (Slice)

Go language slices are an abstraction over arrays.

The length of Go arrays cannot be changed, so in specific scenarios such a collection is not very suitable. Go provides a flexible and powerful built-in type: slice ("dynamic array"). Compared with arrays, the length of a slice is not fixed; elements can be appended, and appending may increase the capacity of the slice.

Defining Slices

You can declare an array of unspecified size to define a slice:

var identifier []type

Slices do not need to specify a length.

Or usemake()Function to create a slice:

var slice1 []type = make([]type, len)

也可以简写为

slice1 := make([]type, len)

You can also specify the capacity, wherecapacityis an optional parameter.

make([]T, length, capacity)

Here len is the length of the array and also the initial length of the slice.

Slice Initialization

s :=[] int {1,2,3 } 

Directly initialize the slice,[]Indicates that it is a slice type,{1,2,3}The initialization values are, in order:1,2,3, itscap=len=3。

s := arr[:] 

Initialize a Slices, is a reference to the array arr.

s := arr[startIndex:endIndex] 

Create a new slice from the elements of arr from index startIndex to endIndex-1.

s := arr[startIndex:] 

When endIndex is defaulted, it means up to the last element of arr.

s := arr[:endIndex] 

When startIndex is defaulted, it means starting from the first element of arr.

s1 := s[startIndex:endIndex] 

Initialize slice s1 through slice s.

s :=make([]int,len,cap) 

Through the built-in functionmake()Initialize a Slices，[]intDenotes a slice whose element type is int.

len() and cap() functions

Slices are indexable, and their length can be obtained by the len() method.

Slices provide the cap() method for calculating capacity, which can measure how long a slice can reach at most.

The following are specific examples:

The output of the above example is:

len=3 cap=5 slice=[0 0 0]

Empty (nil) slice

Before a slice is initialized, it defaults to nil with a length of 0, for example:

The output of the above example is:

len=0 cap=0 slice=[]
切片是空的

Slicing a Slice

You can set lower and upper bounds to slice a slice.[lower-bound:upper-bound], example as follows:

The output of executing the above code is:

len=9 cap=9 slice=[0 1 2 3 4 5 6 7 8]
numbers == [0 1 2 3 4 5 6 7 8]
numbers[1:4] == [1 2 3]
numbers[:3] == [0 1 2]
numbers[4:] == [4 5 6 7 8]
len=0 cap=5 slice=[]
len=2 cap=9 slice=[0 1]
len=3 cap=7 slice=[2 3 4]

append() and copy() functions

If you want to increase the capacity of a slice, you must create a new larger slice and copy the contents of the original slice into it.

The following code describes the copy method for copying slices and the append method for appending new elements to a slice.

The output of executing the above code is:

len=0 cap=0 slice=[]
len=1 cap=1 slice=[0]
len=2 cap=2 slice=[0 1]
len=5 cap=6 slice=[0 1 2 3 4]
len=5 cap=12 slice=[0 1 2 3 4]