Golang variables: Difference between revisions
From wikinotes
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<blockquote> | <blockquote> | ||
<syntaxhighlight lang="go"> | <syntaxhighlight lang="go"> | ||
const myVar := "hi" | const myVar := "hi" // variable that cannot be reassigned | ||
const MyVar := "hi" | const MyVar := "hi" // exported variable, that cannot be reassigned | ||
const myVar = 2 | const myVar = 2 // infer constant type | ||
const ( // group constant assignment | |||
name string = "foo" | |||
age int = 123 | |||
) | |||
// 'iota' will auto-increment the value of the assignment, | |||
// allowing you to use constants similar to an enum | |||
// | |||
// since the type here is inferred, comparing a variable | |||
// with no value to the first entry will return true. | |||
// for this reason, the first const in a iota group is generally reserved as an error | |||
// | |||
// ex. | |||
// const ( red = iota; green; blue ) | |||
// var i int | |||
// i == red // returns true | |||
const ( | |||
invalid = iota | |||
red | |||
green | |||
blue | |||
) | |||
</syntaxhighlight> | </syntaxhighlight> | ||
Revision as of 18:34, 29 May 2022
Assignment
// declare and assign variable var name string name = "foo" // declare and assign var in one step var name string = "foo" // declare and assign variable, inferring type name := "foo"
Constants
const myVar := "hi" // variable that cannot be reassigned const MyVar := "hi" // exported variable, that cannot be reassigned const myVar = 2 // infer constant type const ( // group constant assignment name string = "foo" age int = 123 ) // 'iota' will auto-increment the value of the assignment, // allowing you to use constants similar to an enum // // since the type here is inferred, comparing a variable // with no value to the first entry will return true. // for this reason, the first const in a iota group is generally reserved as an error // // ex. // const ( red = iota; green; blue ) // var i int // i == red // returns true const ( invalid = iota red green blue )There are some rules for constant:
- Constants cannot be assigned at runtime (ex. the result of a function). They must be static at compile time.
- Constants must be assigned a immutable type (ex. collections are mutable, so they cannot be constants)
- Inner scopes can declare the same constant with a new value. It will superseed the outer constant's value while working within that scope.
- If inferring a constant, it's type may take on the type of an operation it is used with. (likely best to explicitly declare type)
Type Conversion
float32(123) == 123. // cast int as float32 string(107) == "k" // retrieve char for 107 in ascii chart strconv.Itoa(107) == "107" // represent 107 as string
Introspection
fmt.Prinf("%T\n", myVar) // print type of myVar
Mutability
Mutable
- Arrays - Maps - Channels - StructsImmutable
- Interfaces - Booleans - Numeric Types - Strings - Pointers