Master Go's Conditional Statements: if, else, and Nested Logic Explained

1.1.1. Go Conditional Statements

Conditional statements let developers specify one or more conditions, test whether they are true, and execute designated statements when true, otherwise execute alternative statements.

Go provides several forms of conditional statements.

1.1.2. if Statement – an if statement consists of a Boolean expression followed by one or more statements.

The syntax of the if statement in Go is as follows:

• Parentheses around the condition expression can be omitted.<br/>• An initialization statement is supported, allowing definition of block‑local variables.<br/>• The opening brace must appear after the condition expression.<br/><br/>if booleanExpression {<br/>    /* executed when the Boolean expression is true */<br/>}<br/>

If the Boolean expression evaluates to true, the following block is executed; otherwise it is skipped.

x := 0<br/><br/>// if x > 10        // Error: missing condition in if statement<br/>// {<br/>// }<br/><br/>if n := "abc"; x > 0 {<br/>    // Initialization statement can be anything, e.g., println("init")<br/>    println(n[2])<br/>} else if x < 0 {<br/>    // Note the position of the opening brace for else if and else<br/>    println(n[1])<br/>} else {<br/>    println(n[0])<br/>}<br/>

* Go does not support the ternary operator (a > b ? a : b).

Example:

package main<br/><br/>import "fmt"<br/><br/>func main() {<br/>   // Define a local variable<br/>   var a int = 10<br/>   // Use an if statement to evaluate a Boolean expression<br/>   if a < 20 {<br/>       // Executed when the condition is true<br/>       fmt.Printf("a is less than 20
")<br/>   }<br/>   fmt.Printf("The value of a is : %d
", a)<br/>}<br/>

The output of the above code is:

a is less than 20<br/>The value of a is : 10<br/>

1.1.3. if...else Statement – an optional else clause executes when the Boolean expression is false.

Syntax

In Go, the syntax of the if...else statement is:

if booleanExpression {<br/>   /* executed when true */<br/>} else {<br/>   /* executed when false */<br/>}<br/>

If the Boolean expression is true, the if block runs; otherwise the else block runs.

Example:

package main<br/><br/>import "fmt"<br/><br/>func main() {<br/>   // Local variable definition<br/>   var a int = 100<br/>   // Evaluate Boolean expression<br/>   if a < 20 {<br/>       fmt.Printf("a is less than 20
")<br/>   } else {<br/>       fmt.Printf("a is not less than 20
")<br/>   }<br/>   fmt.Printf("The value of a is : %d
", a)<br/>}<br/>

The output of the above code is:

a is not less than 20<br/>The value of a is : 100<br/>

1.1.4. Nested if Statements – you can embed one or more if or else if statements inside an if or else if.

Syntax

The syntax for nested if statements in Go is:

if booleanExpression1 {<br/>   /* executed when expression1 is true */<br/>   if booleanExpression2 {<br/>       /* executed when expression2 is true */<br/>   }<br/>}<br/>

You can similarly nest else if…else statements inside an if block.

Example

package main<br/><br/>import "fmt"<br/><br/>func main() {<br/>   var a int = 100<br/>   var b int = 200<br/>   if a == 100 {<br/>       if b == 200 {<br/>           fmt.Printf("a is 100, b is 200
")<br/>       }<br/>   }<br/>   fmt.Printf("a value : %d
", a)<br/>   fmt.Printf("b value : %d
", b)<br/>}<br/>

The output of the above code is:

a is 100, b is 200<br/>a value : 100<br/>b value : 200<br/>

Source: https://www.topgoer.com/流程控制/条件语句if.html

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