# class YAML::Builder

- YAML::Builder
- Reference
- Object

##
Overview

A YAML builder generates valid YAML.

A `YAML::Error` is raised if attempting to generate an invalid YAML (for example, if invoking `#end_sequence` without a matching `#start_sequence`)

    require "yaml"

    string = YAML.build do |yaml|
      yaml.mapping do
        yaml.scalar "foo"
        yaml.sequence do
          yaml.scalar 1
          yaml.scalar 2
        end
        yaml.scalar "bar"
        yaml.mapping do
          yaml.scalar "baz"
          yaml.scalar "qux"
        end
      end
    end
    string # => "---\nfoo:\n- 1\n- 2\nbar:\n  baz: qux\n"

##
Defined in:

yaml/builder.cr

##
Constructors

- .new(io : IO)

  Creates a `YAML::Builder` that will write to the given `IO`.

##
Class Method Summary

- .build(io : IO, & : self -> ) : Nil

  Creates a `YAML::Builder` that writes to io and yields it to the block.

##
Instance Method Summary

- #alias(anchor : String) : Nil

  Emits an alias to the given anchor.

- #close : Nil

  Closes the builder, freeing up resources.

- #document(*, implicit_start_indicator : Bool = false, &)

  Starts a document, invokes the block, and then ends it.

- #end_document

  Ends a document.

- #end_mapping : Nil

  Ends a mapping.

- #end_sequence : Nil

  Ends a sequence.

- #end_stream : Nil

  Ends a YAML stream.

- #finalize
- #flush

  Flushes any pending data to the underlying `IO`.

- #mapping(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::MappingStyle = YAML::MappingStyle::ANY, &)

  Starts a mapping, invokes the block, and then ends it.

- #max_nesting : Int32

  By default the maximum nesting of sequences/mappings is 99.

- #max_nesting=(max_nesting : Int32)

  By default the maximum nesting of sequences/mappings is 99.

- #merge(anchor : String) : Nil

  Emits the scalar `"<<"` followed by an alias to the given anchor.

- #scalar(value, anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::ScalarStyle = YAML::ScalarStyle::ANY)

  Emits a scalar value.

- #sequence(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::SequenceStyle = YAML::SequenceStyle::ANY, &)

  Starts a sequence, invokes the block, and the ends it.

- #start_document(*, implicit_start_indicator : Bool = false)

  Starts a document.

- #start_mapping(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::MappingStyle = YAML::MappingStyle::ANY) : Nil

  Starts a mapping.

- #start_sequence(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::SequenceStyle = YAML::SequenceStyle::ANY) : Nil

  Starts a sequence.

- #start_stream

  Starts a YAML stream.

- #stream(&)

  Starts a YAML stream, invokes the block, and ends it.

### Instance methods inherited from class `Reference`

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

### Constructor methods inherited from class `Reference`

new new, unsafe_construct(address : Pointer, *args, **opts) : self unsafe_construct

### Class methods inherited from class `Reference`

pre_initialize(address : Pointer) pre_initialize

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.new(io : IO) #

Creates a `YAML::Builder` that will write to the given `IO`.

##
Class Method Detail

def self.build(io : IO, & : self -> ) : Nil #

Creates a `YAML::Builder` that writes to io and yields it to the block.

After returning from the block the builder is closed.

##
Instance Method Detail

def alias(anchor : String) : Nil #

Emits an alias to the given anchor.

    require "yaml"

    yaml = YAML.build do |builder|
      builder.mapping do
        builder.scalar "key"
        builder.alias "example"
      end
    end

    yaml # => "---\nkey: *example\n"

def close : Nil #

Closes the builder, freeing up resources.

def document(*, implicit_start_indicator : Bool = false, &) #

Starts a document, invokes the block, and then ends it.

If implicit_start_indicator is true, skips printing the document start indicator (`---`) if this is the first document in the stream.

def end_document #

Ends a document.

def end_mapping : Nil #

Ends a mapping.

def end_sequence : Nil #

Ends a sequence.

def end_stream : Nil #

Ends a YAML stream.

def finalize #
def flush #

Flushes any pending data to the underlying `IO`.

def mapping(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::MappingStyle = YAML::MappingStyle::ANY, &) #

Starts a mapping, invokes the block, and then ends it.

def max_nesting : Int32 #

By default the maximum nesting of sequences/mappings is 99. Nesting more than this will result in a YAML::Error. Changing the value of this property allows more/less nesting.

def max_nesting=(max_nesting : Int32) #

By default the maximum nesting of sequences/mappings is 99. Nesting more than this will result in a YAML::Error. Changing the value of this property allows more/less nesting.

def merge(anchor : String) : Nil #

Emits the scalar `"<<"` followed by an alias to the given anchor.

See YAML Merge.

    require "yaml"

    yaml = YAML.build do |builder|
      builder.mapping do
        builder.merge "development"
      end
    end

    yaml # => "---\n<<: *development\n"

def scalar(value, anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::ScalarStyle = YAML::ScalarStyle::ANY) #

Emits a scalar value.

def sequence(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::SequenceStyle = YAML::SequenceStyle::ANY, &) #

Starts a sequence, invokes the block, and the ends it.

def start_document(*, implicit_start_indicator : Bool = false) #

Starts a document.

If implicit_start_indicator is true, skips printing the document start indicator (`---`) if this is the first document in the stream.

def start_mapping(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::MappingStyle = YAML::MappingStyle::ANY) : Nil #

Starts a mapping.

def start_sequence(anchor : String | Nil = nil, tag : String | Nil = nil, style : YAML::SequenceStyle = YAML::SequenceStyle::ANY) : Nil #

Starts a sequence.

def start_stream #

Starts a YAML stream.

def stream(&) #

Starts a YAML stream, invokes the block, and ends it.