class Prism::WhenNode

Represents the use of the ‘when` keyword within a case statement.

case true
when true



attr_reader conditions: Array


attr_reader keyword_loc: Location


attr_reader statements: StatementsNode?

Public Class Methods

new(keyword_loc, conditions, statements, location) click to toggle source

def initialize: (keyword_loc: Location, conditions: Array, statements: StatementsNode?, location: Location) -> void

# File lib/prism/node.rb, line 16309
def initialize(keyword_loc, conditions, statements, location)
  @keyword_loc = keyword_loc
  @conditions = conditions
  @statements = statements
  @location = location
type() click to toggle source

Similar to type, this method returns a symbol that you can use for splitting on the type of the node without having to do a long === chain. Note that like type, it will still be slower than using == for a single class, but should be faster in a case statement or an array comparison.

def self.type: () -> Symbol

# File lib/prism/node.rb, line 16400
def self.type

Public Instance Methods

accept(visitor) click to toggle source

def accept: (visitor: Visitor) -> void

# File lib/prism/node.rb, line 16317
def accept(visitor)
child_nodes() click to toggle source

def child_nodes: () -> Array[nil | Node]

# File lib/prism/node.rb, line 16322
def child_nodes
  [*conditions, statements]
Also aliased as: deconstruct
comment_targets() click to toggle source

def comment_targets: () -> Array[Node | Location]

# File lib/prism/node.rb, line 16335
def comment_targets
  [keyword_loc, *conditions, *statements]
compact_child_nodes() click to toggle source

def compact_child_nodes: () -> Array

# File lib/prism/node.rb, line 16327
def compact_child_nodes
  compact = []
  compact << statements if statements
copy(**params) click to toggle source

def copy: (**params) -> WhenNode

# File lib/prism/node.rb, line 16340
def copy(**params)
    params.fetch(:keyword_loc) { keyword_loc },
    params.fetch(:conditions) { conditions },
    params.fetch(:statements) { statements },
    params.fetch(:location) { location },
deconstruct() click to toggle source

def deconstruct: () -> Array[nil | Node]

Alias for: child_nodes
deconstruct_keys(keys) click to toggle source

def deconstruct_keys: (keys: Array) -> Hash[Symbol, nil | Node | Array | String | Token | Array | Location]

# File lib/prism/node.rb, line 16353
def deconstruct_keys(keys)
  { keyword_loc: keyword_loc, conditions: conditions, statements: statements, location: location }
inspect(inspector = click to toggle source

def inspect(inspector: NodeInspector) -> String

# File lib/prism/node.rb, line 16363
def inspect(inspector =
  inspector << inspector.header(self)
  inspector << "├── keyword_loc: #{inspector.location(keyword_loc)}\n"
  inspector << "├── conditions: #{inspector.list("#{inspector.prefix}│   ", conditions)}"
  if (statements = self.statements).nil?
    inspector << "└── statements: ∅\n"
    inspector << "└── statements:\n"
    inspector << statements.inspect(inspector.child_inspector("    ")).delete_prefix(inspector.prefix)
keyword() click to toggle source

def keyword: () -> String

# File lib/prism/node.rb, line 16358
def keyword
type() click to toggle source

Sometimes you want to check an instance of a node against a list of classes to see what kind of behavior to perform. Usually this is done by calling ‘[cls1, cls2].include?(node.class)` or putting the node into a case statement and doing `case node; when cls1; when cls2; end`. Both of these approaches are relatively slow because of the constant lookups, method calls, and/or array allocations.

Instead, you can call type, which will return to you a symbol that you can use for comparison. This is faster than the other approaches because it uses a single integer comparison, but also because if you’re on CRuby you can take advantage of the fact that case statements with all symbol keys will use a jump table.

def type: () -> Symbol

# File lib/prism/node.rb, line 16390
def type