String Functions

Among Go's standard libraries, the strings package provides many useful string functions. Let's work with strings through several examples.

1. Search (Contains, Prefix/Suffix, Index)

func TestStrings(t *testing.T) {
	assert.True(t, strings.Contains("test", "st"))
	assert.True(t, strings.ContainsAny("test", "s"))
	assert.True(t, strings.HasPrefix("test", "te"))
	assert.True(t, strings.HasSuffix("test", "st"))
  
  assert.Equal(t, 2, strings.Count("test", "t"))
	assert.Equal(t, 1, strings.Index("test", "e"))
}

2. Replace (Uppercase/Lowercase, Trim, Map)

func TestStrings(t *testing.T) {
	assert.Equal(t, "f00", strings.Replace("foo", "o", "0", -1))
	assert.Equal(t, "test", strings.ToLower("TEST"))
	assert.Equal(t, "TEST", strings.ToUpper("test"))
	assert.Equal(t, "Test", strings.Trim(" Test  ", " "))
	assert.Equal(t, "Test", strings.TrimSpace(" Test  "))
	f := func(r rune) rune {
		return r + 1
	}
	assert.Equal(t, "bc", strings.Map(f, "ab"))
}

The Map function takes a function and a string as arguments and applies the function to each character of the string.

3. Split (Split, Fields)

func TestStrings(t *testing.T) {
	assert.Equal(t, []string{"a", "b", "c"}, strings.Split("a,b,c", ","))
  assert.Equal(t, []string{"t", "e", "s", "t"}, strings.Fields("t\t   e s t"))
}

Fields splits a string around white space characters (as defined by unicode.IsSpace)

4. Concatenate (+, Sprintf, Builder)

The fmt.Sprintf() method returns a string by formatting various types as you want, making it easy to build the string you need.

func TestStrings(t *testing.T) {
	assert.Equal(t, "hello world", "hello"+" world")
	assert.Equal(t, "data: 123", fmt.Sprintf("%s %d", "data:", 123))
	assert.Equal(t, "3.1416", fmt.Sprintf("%.4f", math.Pi))

	var b strings.Builder
	for i := 3; i >= 1; i-- {
		fmt.Fprintf(&b, "%d...", i)
	}
	b.WriteString("end")
	assert.Equal(t, "3...2...1...end", b.String())
}

The methods provided by strings.Builder offer a way to combine strings faster and more efficiently

5. Join (Join, Repeat)

func TestStrings(t *testing.T) {
	assert.Equal(t, "a-b", strings.Join([]string{"a", "b"}, "-"))
	assert.Equal(t, "AAAAA", strings.Repeat("A", 5))
}

6. Format, Convert (strconv)

func TestStrings(t *testing.T) {
	assert.Equal(t, "23", strconv.Itoa(23))
	assert.Equal(t, "ff", strconv.FormatInt(255, 16))

	intValue, _ := strconv.Atoi("23")
	assert.Equal(t, 23, intValue)
}

You can find the examples written here on github.

References

• https://yourbasic.org/golang/string-functions-reference-cheat-sheet/
• http://pyrasis.com/book/GoForTheReallyImpatient/Unit46
• https://mingrammer.com/gobyexample/string-functions/
• http://cloudrain21.com/go-how-to-concatenate-strings
• http://pyrasis.com/book/GoForTheReallyImpatient/Unit46/02
• https://golang.org/pkg/strings/
• https://yourbasic.org/golang/string-functions-reference-cheat-sheet/