02 - On one conditional

Covered in this module:

• if/else
• switch

if/else

These have a very simple structure in Go.

• parentheses are omitted
• curly braces are required
• related if/else clauses continue on the same line as the last closing brace

  i := 5
  if i < 0 {
      fmt.Println("i is negative")
  } else if i > 0 {
      fmt.Println("i is positive")
  } else {
      fmt.Println("i is 0")
  }
  

Note

Go does not have an analog for the ternary operator!

A statement can precede the condition of an if clause. Variables declared in-line are only available within the if/else block

if i := 5; i < 0 {
    fmt.Println("i is negative")
} else if i > 0 {
    fmt.Println("i is positive")
} else {
    fmt.Println("i is 0")
}

// referencing `i` here would fail (this would be caught at compilation)

switch

Switch can be used as an alternative to an if/else:

i := 5
switch {
case i < 0:
    fmt.Println("i is negative")
case i > 0:
    fmt.Println("i is positive")
default:
    fmt.Println("i is 0")
}

Switch can be used for pattern matching. Cases that use the same result can be comma separated. Cases without a result are explicitly skipped.

i := "Monday"
switch i {
case "Monday":
    fmt.Println("Wake up, it’s a beautiful Monday")
case "Tuesday":
    fmt.Println("Hey everybody it’s Tuesday!")
case "Wednesday", "Thursday": // these two cases get the same result
    fmt.Println("Almost Friday")
case "Friday": // skipped
default:
    fmt.Printf("%v is not the best day\n", i)
}

Default is not required but is recommended in cases where your pattern match is not exhaustive. If the switch matches no cases the code will move forward.

Switch can be used to check the type of an interface (interfaces are covered in part 10):

var i interface{}

switch i.(type) {
case string:
    fmt.Println("i is a string")
case bool:
    fmt.Println("i is a boolean")
case int:
    fmt.Println("i is an int")
default:
    fmt.Println("unexpected type")
}

Hands on!

1. In the repo, open the file ./basics/02conditionals.go
2. Complete the TODOs
3. Run make 02 from project root (alternatively, type go run ./02conditionals.go)
4. Example implementation available on solutions branch