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Go - Type Declarations

Type declarations come in two forms: alias declarations and type definitions.

Alias Declaration

A type alias creates a new name for an existing type.

go
// Alias declaration syntax (An equal sign is used).
type Alias = ExistingType

Examples:

go
// An alias for int64 named Timestamp.
// Timestamp and int64 are identical types.
type Timestamp = int64
// Declare multiple type aliases.
type (
  nodeList = []*Node // nodeList and []*Node are identical types
  Score    = int     // Score and int are identical types
)

Type Definition

A type definition creates a new, distinct type, it is different from any other type including the type it’s created from and may have methods associated with it.

go
// Type definition syntax.
type NewType ExistingType

Examples:

go
// New type named Duration based on int64.
// Duration and int64 are different types.
type Duration int64
// Define multiple types.
// All the defined types are different from the types they're created from.
type (
  TimeZone  int
  ByteSlice []byte
  Point     struct{ x, y float64 }
)