Psych::Handler

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

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 110
def alias anchor
end
            

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

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 236
def empty
end
            

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.

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 93
def end_document implicit
end
            

Called when a map ends

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 230
def end_mapping
end
            

Called when a sequence ends.

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 191
def end_sequence
end
            

Called when the YAML stream ends

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 241
def end_stream
end
            

Called before each event with line/column information.

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 246
def event_location(start_line, start_column, end_line, end_column)
end
            

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 indicating 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    ]

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 150
def scalar value, anchor, tag, plain, quoted, style
end
            

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

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 72
def start_document version, tag_directives, implicit
end
            

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     ]

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 225
def start_mapping anchor, tag, implicit, style
end
            

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     ]

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 186
def start_sequence anchor, tag, implicit, style
end
            

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.

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 47
def start_stream encoding
end
            

Is this handler a streaming handler?

 
               # File ruby-3.1.2/ext/psych/lib/psych/handler.rb, line 251
def streaming?
  false
end