Conditions

If-else Statement

Executes a block when a condition evaluates to true.

if condition {
    // runs if condition is true
} else if anotherCondition {
    // runs if it gets here and this condition is true
} else {
    // runs if none of the above are true
}

• Variable declaration is allowed inside the if statement, with scope limited to the if-else block:

  s := "Hello"
  
  if n := len(s); n == 1 {
  	fmt.Println("n is:", n)
  } else if n >= 2 {
  	fmt.Println("n is:", n)
  } else {
  	fmt.Println("Empty string", n)
  }
  
  // n is: 5
  
  fmt.Println("n is:", n) // <-- compiler: undefined: n

Switch Statement

Executes the block for the first matching case.

switch expression {
case value1:
    // runs if expression == value1
case value2:
    // runs if expression == value2
case value3, value4:
    // runs if expression == value3 or value4
default:
    // runs if no case matches
}

Each case ends with an implicit break (the keyword itself can still be used).

• fallthrough overrides the implicit break and continues into the next case:

  a := 2
  
  switch a {
  case 1:
      fmt.Println("One")
  case 2:
      fmt.Println("Two")
      fallthrough
  case 3:
      fmt.Println("Three")
  case 4:
      fmt.Println("Four")
  default:
      fmt.Println("None of above")
  }
  
  // Two
  // Three

• Variable declaration is allowed inside the switch statement, with scope limited to the switch block:

  s := "hi"
  
  switch n := len(s); n {
  case 1:
  	fmt.Println("n is:", n)
  case 2:
  	fmt.Println("n is:", n)
  default:
  	fmt.Println("None of above", n)
  }
  
  // n is: 2
  
  fmt.Println("n is:", n) // <-- compiler: undefined: n

• Omitting the expression makes switch behave like an if-else chain.

  a := 3
  
  switch {
  case a == 1:
      fmt.Println("One")
  case a == 2:
      fmt.Println("Two")
  case a == 3 || a == 4:
      fmt.Println("Three or Four")
  default:
      fmt.Println("None of above")
  }
  
  // Three or Four