Composable#static

[ismasan]

#static

A type that always returns a valid, static value, regardless of input.

ten = Types::Integer.static(10)
ten.parse(10) # => 10
ten.parse(100) # => 10
ten.parse('hello') # => 10
ten.parse() # => 10
ten.metadata[:type] # => Integer

Useful for data structures where some fields shouldn't change. Example:

CreateUserEvent = Types::Hash[
  type: Types::String.static('CreateUser'),
  name: String,
  age: Integer
]

Note that the value must be of the same type as the starting step's target type.

Types::Integer.static('nope') # raises ArgumentError

This usage is the same as using Types::Static['hello']directly.

Block usage

Passing a proc will evaluate the proc on every invocation. Use this for generated values.

random_number = Types::Numeric.static { rand }
random_number.parse # 0.32332
random_number.parse('foo') # 0.54322 etc

Note that in this mode, the type of generated value must match the initial step's type, validated at invocation.

random_number = Types::String.static { rand } # this won't raise an error here
random_number.parse # raises Plumb::ParseError because `rand` is not a String