Strings, Arrays and Slices

📝 Useful code snippets for strings

Changing a character in a string

Strings are immutable, so in fact a new string is created here.

str := "hello"
c := []rune(str)
c[0] = 'c'
s2 := string(c) // s2 == "cello"

Taking a part (substring) of a string

substr := str[n:m]

Looping over a string with for or for-range

// gives only the bytes:
for i:=0; i < len(str); i++ {
  ... = str[i]
}
// gives the Unicode characters:
for ix, ch := range str {
  ...
}

Finding number of bytes and characters in string

Number of bytes in a string str:

len(str)

Number of characters in a string str:

The fastest way is:

utf8.RuneCountInString(str)

An equivalent way is:

len([]int(str))

Concatenating strings

The fastest way is:

// with a bytes.Buffer 
var buffer bytes.Buffer
var s string
buffer.WriteString(s)
fmt.Print(buffer.String(), "\n")

Other ways are:

Strings.Join() // using Join function
str1 += str2 // using += operator

📝 Useful code snippets for arrays and slices

Creation

To create an array:

arr1 := new([len]type)

To create a slice:

slice1 := make([]type, len)

Initialization

To initialize an array:

arr1 := [...]type{i1, i2, i3, i4, i5}
arrKeyValue := [len]type{i1: val1, i2: val2}

To initialize a slice:

var slice1 []type = arr1[start:end]

Cutting the last element of an array or slice line

line = line[:len(line)-1]

Looping over an array (or slice) arr with for or for-range

for i:=0; i < len(arr); i++ {
  ... = arr[i]
}

for ix, value := range arr {
  ...
}

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This pretty much summarizes arrays, strings, and slices. The next lesson deals with structs, interfaces, and maps.