SoFunction
Updated on 2025-03-05

In-depth analysis of Go statements and expressions case manual

Statement

A statement is a single logical instruction in the Go programming language that completes a specific operation. Statements are the basic units that make up programs, they can control program flow, assign values, declare variables, etc.

1. Declaration statement

1.1 Variable declaration

Used to define one or more variables, but do not necessarily have to be assigned values.

Give an example

var age int
var name, address string

1.2 Constant declaration

Defines one or more constant values.

Give an example

const PI = 3.14
const greeting = "Hello, Go!"

2. Assignment statement

Used to assign new values ​​to declared variables.

Give an example

x := 10
y = x + 5
a, b := 20, 30

3. Control flow statement

3.1 Conditional Statement

if statement

Execute code blocks based on a certain condition.

Give an example

if x > y {
    ("x is greater than y")
} else if x < y {
    ("x is less than y")
} else {
    ("x is equal to y")
}

Switch statement

Execute one of multiple code blocks based on an expression or value.

Give an example

switch grade {
case "A":
    ("Excellent!")
case "B":
    ("Good")
default:
    ("Passed")
}

3.2 Loop statements

for statement

Used to repeatedly execute a piece of code.

Give an example

for i := 0; i < 10; i++ {
    (i)
}
for _, value := range array {
    (value)
}

3.3 Jump statement

break statement

Used to interrupt the current loop.

Give an example

for i := 0; i < 10; i++ {
    if i == 5 {
        break
    }
    (i)
}

Continue statement

Skip the current iteration and continue with the next iteration.

Give an example

for i := 0; i < 10; i++ {
    if i%2 == 0 {
        continue
    }
    (i)
}

Return statement

Returns a specific value from the function.

Give an example

func add(a int, b int) int {
    return a + b
}

goto statement

Jump to the specified tag.

Give an example

for i := 0; i < 10; i++ {
    if i == 5 {
        goto end
    }
    (i)
end:
}

4. Other statements

4.1 defer statement

Make sure to execute a statement before the function ends.

Give an example

func printFile() {
    file, err := ("")
    if err != nil {
        panic(err)
    }
    defer ()
    
    // Do file operations...
}

4.2 go statement

Execute function calls in a new goroutine.

Give an example

go func() {
    ("Executing in a new goroutine")
}()

Practical cases

Statement Statement example
Variable declaration var age int、var name, address string、var x, y int = 3, 4、var active bool、var salary = 50000
Constant declaration const PI = 3.14、const greeting = "Hello, Go!"、const active = false、const daysInWeek = 7、const lightSpeed = 299792458
Assignment statement x := 10、y = x + 5、a, b := 20, 30、name = "Alice"、isActive := true
if statement if x > 10 { ... }、if x > 10 && y < 5 { ... }、if active { ... }、if name := getName(); name != "" { ... }、if age > 18 { ... } else { ... }
Switch statement switch x { ... }、switch { case x > 10: ... }、switch day { case "Monday": ... }、switch n := 4; n { ... }、switch y.(type) { ... }
for statement for i := 0; i < 5; i++ { ... }、for i, v := range arr { ... }、for x > 5 { ... }、for key, val := range mapData { ... }、for _, char := range str { ... }
break statement for { if condition { break } }、switch { case x: if y { break } }、for x > 10 { ...; break; ... }、label: for { ...; break label; ... }、for i := 0; i < 10; i++ { if i == 5 { break } }
Continue statement for i := 0; i < 10; i++ { if i%2 == 0 { continue } }、for _, v := range data { if v == nil { continue } }、for x > 0 { ...; if condition { continue } ... }、for { if !isValid(data) { continue } ... }、for idx, value := range items { if value == "" { continue } }
Return statement func add(a, b int) int { return a + b }、func name() string { return "Alice" }、func getDetails() (string, int) { return "Alice", 30 }、func isActive() bool { ...; return false }、func calculate() float64 { ...; return result }
goto statement label1: for { ...; if x > 5 { goto label1 } }、label2: ("Start"); ...; goto label2、if condition { goto errorHandling } ... errorHandling: ...、if !isValid { goto cleanup } ... cleanup: ...
defer statement file, _ := (""); defer ()、(); defer ()、defer ("Finished!")、(); defer ()、reader := openReader(); defer ()
Go statement go ("Running in goroutine")、go process(data)、go func(val int) { ... }(x)、go startServer()、go handleRequest(request)

Introduction, detailed explanation, examples of expressions

In programming, an expression is a structure that combines variables, constants, and operators in some way and can be evaluated as a certain value. In Go, expressions can take many forms depending on the content and results it contains.

1. Basic expressions

1.1 Literal

A literal is an expression that represents a fixed value.

Give an example

42       // Integer literal3.14     // Floating point literaltrue     // Boolean literal"Hello"  // String literal

1.2 Variables and constants

Variables and constants are predefined entities with specific names and values.

Give an example

const PI = 3.14
var name = "Go"

2. Compound expressions

2.1 Arithmetic expressions

These expressions use arithmetic operators such as +, -, *, / and %.

Give an example

a := 5
b := 2
sum := a + b        // Results: 7difference := a - b // Results: 3product := a * b    // Results: 10quotient := a / b   // Results: 2remainder := a % b  // result：1

2.2 Relational expressions

Relational expressions are evaluated as Boolean values, and commonly used relational operators are ==, !=, <, <=, > and >=.

Give an example

x := 5
y := 3
result1 := x == y  // Result: falseresult2 := x &gt; y   // result：true

2.3 Logical expressions

Logical expressions are used to combine multiple Boolean expressions. Commonly used logical operators are &&, || and!.

Give an example

a := true
b := false
result1 := a &amp;&amp; b  // Result: falseresult2 := a || b  // Result: trueresult3 := !a     // result：false

2.4 Assignment expressions

The assignment expression assigns a value to the variable and returns the value.

Give an example

x := 10           // Use := for assignmenty = x + 5         // use = Perform assignment

3. Function call expression

The function call returns the return value of the function.

Give an example

func add(a int, b int) int {
    return a + b
}
result := add(5, 3)  // result：8

4. Type conversion expression

These expressions convert values ​​from one type to another.

Give an example

x := 5.8
y := int(x)  // result：5

Practical cases

Statement Statement example
Variable declaration var age int、var name, address string、var x, y int = 3, 4、var active bool、var salary = 50000
Constant declaration const PI = 3.14、const greeting = "Hello, Go!"、const active = false、const daysInWeek = 7、const lightSpeed = 299792458
Assignment statement x := 10、y = x + 5、a, b := 20, 30、name = "Alice"、isActive := true
if statement if x > 10 { ... }、if x > 10 && y < 5 { ... }、if active { ... }、if name := getName(); name != "" { ... }、if age > 18 { ... } else { ... }
Switch statement switch x { ... }、switch { case x > 10: ... }、switch day { case "Monday": ... }、switch n := 4; n { ... }、switch y.(type) { ... }
for statement for i := 0; i < 5; i++ { ... }、for i, v := range arr { ... }、for x > 5 { ... }、for key, val := range mapData { ... }、for _, char := range str { ... }
break statement for { if condition { break } }、switch { case x: if y { break } }、for x > 10 { ...; break; ... }、label: for { ...; break label; ... }、for i := 0; i < 10; i++ { if i == 5 { break } }
Continue statement for i := 0; i < 10; i++ { if i%2 == 0 { continue } }、for _, v := range data { if v == nil { continue } }、for x > 0 { ...; if condition { continue } ... }、for { if !isValid(data) { continue } ... }、for idx, value := range items { if value == "" { continue } }
Return statement func add(a, b int) int { return a + b }、func name() string { return "Alice" }、func getDetails() (string, int) { return "Alice", 30 }、func isActive() bool { ...; return false }、func calculate() float64 { ...; return result }
goto statement label1: for { ...; if x > 5 { goto label1 } }、label2: ("Start"); ...; goto label2、if condition { goto errorHandling } ... errorHandling: ...、if !isValid { goto cleanup } ... cleanup: ...
defer statement file, _ := (""); defer ()、(); defer ()、defer ("Finished!")、(); defer ()、reader := openReader(); defer ()
Go statement go ("Running in goroutine")、go process(data)、go func(val int) { ... }(x)、go startServer()、go handleRequest(request)

The above is the detailed content of the in-depth analysis of the Go statement and expression case manual. For more information about Go statement expression cases, please pay attention to my other related articles!