The functions that handle strings in go are mainly in the strings and Strconv packages.

Strings and strconv bag

As a basic data structure, every language has some predefined handling functions for strings. The Strings package is used in Go to perform major operations on strings.

Prefixes and suffixes

HasPrefix Checks whether the string s starts with prefix:

strings.HasPrefix(s, prefix string) bool
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HasSuffix Checks whether string S ends with suffix:

strings.HasSuffix(s, suffix string) bool
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The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	var str string = "This is an example of a string"
	fmt.Printf("T/F? Does the string \"%s\" have prefix %s? ", str, "Th")
	fmt.Printf("%t\n", strings.HasPrefix(str, "Th"))}Copy the code

Output:

T/F? Does the string "This is an example of a string" have prefix Th? true
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This example also demonstrates the use of the escape character \ and formatting strings.

String inclusion relation

Contains Determines whether the string s Contains substr:

strings.Contains(s, substr string) bool
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Determine the position of the substring or character in the parent string (index)

Index returns the Index of the string STR in string s (the Index of the first character of STR), -1 means that string S does not contain string STR:

strings.Index(s, str string) int
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LastIndex Returns the index of the last occurrence of STR in string s (the index of the first character of STR), -1 means that string S does not contain STR:

strings.LastIndex(s, str string) int
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If you need to query the position of non-ASCII characters in the parent string, you are advised to use the following functions to locate characters:

strings.IndexRune(s string, r rune) int
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Note: If ch is a non-ASCII character use strings.IndexRune(s string, Ch int) int." This method is defined in the latest version of Go as func IndexRune(s string, r rune) int. The actual use of the second parameter rune can be either rune or int, For example strings.indexrune ("chicken", 99) or strings.indexrune ("chicken", rune('k'))Copy the code

The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	var str string = "Hi, I'm Marc, Hi."

	fmt.Printf("The position of \"Marc\" is: ")
	fmt.Printf("%d\n", strings.Index(str, "Marc"))

	fmt.Printf("The position of the first instance of \"Hi\" is: ")
	fmt.Printf("%d\n", strings.Index(str, "Hi"))
	fmt.Printf("The position of the last instance of \"Hi\" is: ")
	fmt.Printf("%d\n", strings.LastIndex(str, "Hi"))

	fmt.Printf("The position of \"Burger\" is: ")
	fmt.Printf("%d\n", strings.Index(str, "Burger"))}Copy the code

Output:

The position of "Marc" is: 8
The position of the first instance of "Hi" is: 0
The position of the last instance of "Hi" is: 14
The position of "Burger" is: -1
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String substitution

Replace replaces the first n strings old in string STR with string new and returns a new string, replacing all strings old with string new if n = -1:

strings.Replace(str, old, new, n) string
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Statistics the number of occurrences of a string

Count is used to Count the number of non-overlapping occurrences of the string STR in the string s:

strings.Count(s, str string) int
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The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	var str string = "Hello, how is it going, Hugo?"
	var manyG = "gggggggggg"

	fmt.Printf("Number of H's in %s is: ", str)
	fmt.Printf("%d\n", strings.Count(str, "H"))

	fmt.Printf("Number of double g's in %s is: ", manyG)
	fmt.Printf("%d\n", strings.Count(manyG, "gg"))}Copy the code

Output:

Number of H's in Hello, how is it going, Hugo? Is: 2 Number of double g's in GGGGGGGG is: 5Copy the code

Repeated string

Repeat is used to Repeat the string s count times and return a new string:

strings.Repeat(s, count int) string
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The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	var origS string = "Hi there! "
	var newS string

	newS = strings.Repeat(origS, 3)
	fmt.Printf("The new repeated string is: %s\n", newS)
}
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Output:

The new repeated string is: Hi there! Hi there! Hi there!
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Changing the case of strings

ToLower converts all Unicode characters in a string to their corresponding lowercase characters:

strings.ToLower(s) string
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ToUpper converts all Unicode characters in a string to their corresponding uppercase characters:

strings.ToUpper(s) string
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The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	var orig string = "Hey, how are you George?"
	var lower string
	var upper string

	fmt.Printf("The original string is: %s\n", orig)
	lower = strings.ToLower(orig)
	fmt.Printf("The lowercase string is: %s\n", lower)
	upper = strings.ToUpper(orig)
	fmt.Printf("The uppercase string is: %s\n", upper)
}
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Output:

The original string is: Hey, how are you George?
The lowercase string is: hey, how are you george?
The uppercase string is: HEY, HOW ARE YOU GEORGE?
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Trim string

You can use strings.trimspace (s) to strip out whitespace at the beginning and end of strings; If you want to strip out specified characters, use strings.Trim(s, “cut”) to strip out the leading and trailing cuts. The second argument to this function can contain any character. If you want to eliminate the beginning or end of the string, you can use TrimLeft or TrimRight to do so.

Split string

Strings.fields (s) will split the string into chunks using one or more whitespace characters as dynamic length delimiters and return a slice, or a slice of length 0 if the string contains only whitespace characters.

Strings.split (s, sep) is used to customize the Split symbol to Split the specified string, also returning slice.

Because both of these functions return slice, it is customary to use a for-range loop to process them (Section 7.3, p.

Concatenate slice into a string

Join is used to concatenate slice of string element type into a string using a split symbol:

strings.Join(sl []string, sep string) string
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The sample

package main

import (
	"fmt"
	"strings"
)

func main(a) {
	str := "The quick brown fox jumps over the lazy dog"
	sl := strings.Fields(str)
	fmt.Printf("Splitted in slice: %v\n", sl)
	for _, val := range sl {
		fmt.Printf("%s - ", val)
	}
	fmt.Println()
	str2 := "GO1|The ABC of Go|25"
	sl2 := strings.Split(str2, "|")
	fmt.Printf("Splitted in slice: %v\n", sl2)
	for _, val := range sl2 {
		fmt.Printf("%s - ", val)
	}
	fmt.Println()
	str3 := strings.Join(sl2,";")
	fmt.Printf("sl2 joined by ; : %s\n", str3)
}
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Output:

Splitted in slice: [The quick brown fox jumps over the lazy dog] The - quick - brown - fox - jumps - over - the - lazy - dog - Splitted in slice: [GO1 The ABC of Go 25] GO1 - The ABC of Go - 25 - sl2 joined by ; : GO1; The ABC of Go; 25Copy the code

For additional documentation on string manipulation, see the official documentation.

Reads from a string

The strings.NewReader(STR) function is used to generate a Reader, read the contents of the string, and then return a pointer to that Reader.

Read()Read from []byte.
ReadByte() 和 ReadRune()Reads the next byte or rune from the string.

String conversion to other types

String-related conversions are implemented through the Strconv package.

The package contains variables to get the number of bits of int on the operating system on which the program is running, such as strconv.intsize.

The conversion of any type T to a string is always successful.

For converting from numeric types to strings, Go provides the following functions:

strconv.Itoa(i int) stringReturns the string decimal number represented by the number I.
strconv.FormatFloat(f float64, fmt byte, prec int, bitSize int) stringConverts a 64-bit floating-point number to a string, wherefmtPresentation format (whose value can be'b','e','f' 或 'g'),precDenotes precision,bitSizeIn this case, 32 indicates float32 and 64 indicates float64.

Converting a string to another type of TP is not always possible, and error parsing “… “may be thrown at runtime. : invalid argument.

For converting from a string to a number, Go provides the following functions:

strconv.Atoi(s string) (i int, err error)Converts a string to int.
strconv.ParseFloat(s string, bitSize int) (f float64, err error)Converts a string to float64.

Taking advantage of the multi-return nature, these functions return two values, the first being the result of the conversion (if successful) and the second being the possible error. Therefore, we generally use the following form to convert from a string to another type:

val, err = strconv.Atoi(s)
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In the following example, we ignore possible conversion errors:

The sample

package main

import (
	"fmt"
	"strconv"
)

func main(a) {
	var orig string = "666"
	var an int
	var newS string

	fmt.Printf("The size of ints is: %d\n", strconv.IntSize)	  

	an, _ = strconv.Atoi(orig)
	fmt.Printf("The integer is: %d\n", an) 
	an = an + 5
	newS = strconv.Itoa(an)
	fmt.Printf("The new string is: %s\n", newS)
}
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Output:

64-bit system: The size of INts is: 64 32-bit system: The size of INts is: 32 The INTEGER is: 666 The new string is: 671Copy the code

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Go commonly used string handling functions | Go on topic

Strings and strconv bag

Prefixes and suffixes

String inclusion relation

Determine the position of the substring or character in the parent string (index)

String substitution

Statistics the number of occurrences of a string

Repeated string

Changing the case of strings

Trim string

Split string

Concatenate slice into a string

Reads from a string

String conversion to other types

Go commonly used string handling functions | Go on topic

Strings and strconv bag

Prefixes and suffixes

String inclusion relation

Determine the position of the substring or character in the parent string (index)

String substitution

Statistics the number of occurrences of a string

Repeated string

Changing the case of strings

Trim string

Split string

Concatenate slice into a string

Reads from a string

String conversion to other types

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