# class Prism::ParametersNode

Represents the list of parameters on a method, block, or lambda definition.

    def a(b, c, d)
          ^^^^^^^
    end

### Attributes

block[R]

attr_reader block: `BlockParameterNode`?

keyword_rest[R]

attr_reader `keyword_rest`: `Node`?

keywords[R]

attr_reader keywords: Array

optionals[R]

attr_reader optionals: Array

posts[R]

attr_reader posts: Array

requireds[R]

attr_reader requireds: Array

rest[R]

attr_reader rest: `Node`?

### Public Class Methods

new(requireds, optionals, rest, posts, keywords, keyword_rest, block, location) click to toggle source

def initialize: (requireds: Array, optionals: Array, rest: `Node`?, posts: Array, keywords: Array, `keyword_rest`: `Node`?, block: `BlockParameterNode`?, location: `Location`) -> void

    # File lib/prism/node.rb, line 13187
    def initialize(requireds, optionals, rest, posts, keywords, keyword_rest, block, location)
      @requireds = requireds
      @optionals = optionals
      @rest = rest
      @posts = posts
      @keywords = keywords
      @keyword_rest = keyword_rest
      @block = block
      @location = location
    end

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 13300
    def self.type
      :parameters_node
    end

### Public Instance Methods

accept(visitor) click to toggle source

def accept: (visitor: `Visitor`) -> void

    # File lib/prism/node.rb, line 13199
    def accept(visitor)
      visitor.visit_parameters_node(self)
    end

child_nodes() click to toggle source

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

    # File lib/prism/node.rb, line 13204
    def child_nodes
      [*requireds, *optionals, rest, *posts, *keywords, keyword_rest, block]
    end

Also aliased as: deconstruct
comment_targets() click to toggle source

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

    # File lib/prism/node.rb, line 13222
    def comment_targets
      [*requireds, *optionals, *rest, *posts, *keywords, *keyword_rest, *block]
    end

compact_child_nodes() click to toggle source

def `compact_child_nodes`: () -> Array

    # File lib/prism/node.rb, line 13209
    def compact_child_nodes
      compact = []
      compact.concat(requireds)
      compact.concat(optionals)
      compact << rest if rest
      compact.concat(posts)
      compact.concat(keywords)
      compact << keyword_rest if keyword_rest
      compact << block if block
      compact
    end

copy(**params) click to toggle source

def copy: (**params) -> `ParametersNode`

    # File lib/prism/node.rb, line 13227
    def copy(**params)
      ParametersNode.new(
        params.fetch(:requireds) { requireds },
        params.fetch(:optionals) { optionals },
        params.fetch(:rest) { rest },
        params.fetch(:posts) { posts },
        params.fetch(:keywords) { keywords },
        params.fetch(:keyword_rest) { keyword_rest },
        params.fetch(:block) { block },
        params.fetch(:location) { location },
      )
    end

deconstruct()

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 13244
    def deconstruct_keys(keys)
      { requireds: requireds, optionals: optionals, rest: rest, posts: posts, keywords: keywords, keyword_rest: keyword_rest, block: block, location: location }
    end

inspect(inspector = NodeInspector.new) click to toggle source

def inspect(inspector: NodeInspector) -> `String`

    # File lib/prism/node.rb, line 13249
    def inspect(inspector = NodeInspector.new)
      inspector << inspector.header(self)
      inspector << "├── requireds: #{inspector.list("#{inspector.prefix}│   ", requireds)}"
      inspector << "├── optionals: #{inspector.list("#{inspector.prefix}│   ", optionals)}"
      if (rest = self.rest).nil?
        inspector << "├── rest: ∅\n"
      else
        inspector << "├── rest:\n"
        inspector << rest.inspect(inspector.child_inspector("│   ")).delete_prefix(inspector.prefix)
      end
      inspector << "├── posts: #{inspector.list("#{inspector.prefix}│   ", posts)}"
      inspector << "├── keywords: #{inspector.list("#{inspector.prefix}│   ", keywords)}"
      if (keyword_rest = self.keyword_rest).nil?
        inspector << "├── keyword_rest: ∅\n"
      else
        inspector << "├── keyword_rest:\n"
        inspector << keyword_rest.inspect(inspector.child_inspector("│   ")).delete_prefix(inspector.prefix)
      end
      if (block = self.block).nil?
        inspector << "└── block: ∅\n"
      else
        inspector << "└── block:\n"
        inspector << block.inspect(inspector.child_inspector("    ")).delete_prefix(inspector.prefix)
      end
      inspector.to_str
    end

signature() click to toggle source

Mirrors the `Method#parameters` method.

    # File lib/prism/node_ext.rb, line 149
    def signature
      names = []

      requireds.each do |param|
        names << (param.is_a?(MultiTargetNode) ? [:req] : [:req, param.name])
      end

      optionals.each { |param| names << [:opt, param.name] }
      names << [:rest, rest.name || :*] if rest

      posts.each do |param|
        names << (param.is_a?(MultiTargetNode) ? [:req] : [:req, param.name])
      end

      # Regardless of the order in which the keywords were defined, the required
      # keywords always come first followed by the optional keywords.
      keyopt = []
      keywords.each do |param|
        if param.is_a?(OptionalKeywordParameterNode)
          keyopt << param
        else
          names << [:keyreq, param.name]
        end
      end

      keyopt.each { |param| names << [:key, param.name] }

      case keyword_rest
      when ForwardingParameterNode
        names.concat([[:rest, :*], [:keyrest, :**], [:block, :&]])
      when KeywordRestParameterNode
        names << [:keyrest, keyword_rest.name || :**]
      when NoKeywordsParameterNode
        names << [:nokey]
      end

      names << [:block, block.name || :&] if block
      names
    end

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 13290
    def type
      :parameters_node
    end