Class: Psych::Handler

Inherits:
Object show all
Defined in:
lib/psych/handler.rb,
psych_emitter.c

Overview

Psych::Handler is an abstract base class that defines the events used when dealing with Psych::Parser. Clients who want to use Psych::Parser should implement a class that inherits from Psych::Handler and define events that they can handle.

Psych::Handler defines all events that Psych::Parser can possibly send to event handlers.

See Psych::Parser for more details

Direct Known Subclasses

Emitter, Psych::Handlers::Recorder, TreeBuilder

Defined Under Namespace

Classes: DumperOptions

Constant Summary collapse

OPTIONS =

Default dumping options

DumperOptions.new
EVENTS =

Events that a Handler should respond to.

[ :alias,
:empty,
:end_document,
:end_mapping,
:end_sequence,
:end_stream,
:scalar,
:start_document,
:start_mapping,
:start_sequence,
:start_stream ]

Instance Method Summary collapse

Instance Method Details

#alias(anchor) ⇒ Object

Called when an alias is found to anchor. anchor will be the name of the anchor found.

Example

Here we have an example of an array that references itself in YAML:

--- &ponies
- first element
- *ponies

&ponies is the achor, *ponies is the alias. In this case, alias is called with “ponies”.


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# File 'lib/psych/handler.rb', line 109

def alias anchor
end

#emptyObject

Called when an empty event happens. (Which, as far as I can tell, is never).


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# File 'lib/psych/handler.rb', line 235

def empty
end

#end_document(implicit) ⇒ Object

Called with the document ends. implicit is a boolean value indicating whether or not the document has an implicit ending.

Example

Given the following YAML:

---
  hello world

implicit will be true. Given this YAML:

---
  hello world
...

implicit will be false.


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# File 'lib/psych/handler.rb', line 92

def end_document implicit
end

#end_mappingObject

Called when a map ends


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# File 'lib/psych/handler.rb', line 229

def end_mapping
end

#end_sequenceObject

Called when a sequence ends.


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# File 'lib/psych/handler.rb', line 190

def end_sequence
end

#end_streamObject

Called when the YAML stream ends


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# File 'lib/psych/handler.rb', line 240

def end_stream
end

#scalar(value, anchor, tag, plain, quoted, style) ⇒ Object

Called when a scalar value is found. The scalar may have an anchor, a tag, be implicitly plain or implicitly quoted

value is the string value of the scalar anchor is an associated anchor or nil tag is an associated tag or nil plain is a boolean value quoted is a boolean value style is an integer idicating the string style

See the constants in Psych::Nodes::Scalar for the possible values of style

Example

Here is a YAML document that exercises most of the possible ways this method can be called:

---
- !str "foo"
- &anchor fun
- many
  lines
- |
  many
  newlines

The above YAML document contains a list with four strings. Here are the parameters sent to this method in the same order:

# value               anchor    tag     plain   quoted  style
["foo",               nil,      "!str", false,  false,  3    ]
["fun",               "anchor", nil,    true,   false,  1    ]
["many lines",        nil,      nil,    true,   false,  1    ]
["many\nnewlines\n",  nil,      nil,    false,  true,   4    ]

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# File 'lib/psych/handler.rb', line 149

def scalar value, anchor, tag, plain, quoted, style
end

#start_document(version, tag_directives, implicit) ⇒ Object

Called when the document starts with the declared version, tag_directives, if the document is implicit.

version will be an array of integers indicating the YAML version being dealt with, tag_directives is a list of tuples indicating the prefix and suffix of each tag, and implicit is a boolean indicating whether the document is started implicitly.

Example

Given the following YAML:

%YAML 1.1
%TAG ! tag:tenderlovemaking.com,2009:
--- !squee

The parameters for start_document must be this:

version         # => [1, 1]
tag_directives  # => [["!", "tag:tenderlovemaking.com,2009:"]]
implicit        # => false

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# File 'lib/psych/handler.rb', line 71

def start_document version, tag_directives, implicit
end

#start_mapping(anchor, tag, implicit, style) ⇒ Object

Called when a map starts.

anchor is the anchor associated with the map or nil. tag is the tag associated with the map or nil. implicit is a boolean indicating whether or not the map was implicitly started. style is an integer indicating the mapping style.

See the constants in Psych::Nodes::Mapping for the possible values of style.

Example

Here is a YAML document that exercises most of the possible ways this method can be called:

---
k: !!map { hello: world }
v: &pewpew
  hello: world

The above YAML document consists of three maps, an outer map that contains two inner maps. Below is a matrix of the parameters sent in order to represent these three maps:

# anchor    tag                       implicit  style
[nil,       nil,                      true,     1     ]
[nil,       "tag:yaml.org,2002:map",  false,    2     ]
["pewpew",  nil,                      true,     1     ]

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# File 'lib/psych/handler.rb', line 224

def start_mapping anchor, tag, implicit, style
end

#start_sequence(anchor, tag, implicit, style) ⇒ Object

Called when a sequence is started.

anchor is the anchor associated with the sequence or nil. tag is the tag associated with the sequence or nil. implicit a boolean indicating whether or not the sequence was implicitly started. style is an integer indicating the list style.

See the constants in Psych::Nodes::Sequence for the possible values of style.

Example

Here is a YAML document that exercises most of the possible ways this method can be called:

---
- !!seq [
  a
]
- &pewpew
  - b

The above YAML document consists of three lists, an outer list that contains two inner lists. Here is a matrix of the parameters sent to represent these lists:

# anchor    tag                       implicit  style
[nil,       nil,                      true,     1     ]
[nil,       "tag:yaml.org,2002:seq",  false,    2     ]
["pewpew",  nil,                      true,     1     ]

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# File 'lib/psych/handler.rb', line 185

def start_sequence anchor, tag, implicit, style
end

#start_stream(encoding) ⇒ Object

Called with encoding when the YAML stream starts. This method is called once per stream. A stream may contain multiple documents.

See the constants in Psych::Parser for the possible values of encoding.


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# File 'lib/psych/handler.rb', line 46

def start_stream encoding
end

#streaming?Boolean

Is this handler a streaming handler?

Returns:

  • (Boolean)

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# File 'lib/psych/handler.rb', line 245

def streaming?
  false
end