feat(visitor): allow to create custom object (instead of Hash) according to context #299
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This is necessary to create custom object as mapping instead of Hash.
For example, if you prefer `hashobj.key` instead of `hashobj['key']`:
## allows `h.foo` instead of `h['foo']`
class MagicHash < Hash
def method_missing(method, *args)
return super unless args.empty?
return self[method.to_s]
end
end
## override to generate MagicHash instead of Hash
class MagicVisitor < Psych::Visitors::ToRuby
def empty_mapping(o)
MagicHash.new
end
end
## example to access `ydoc.foo` instead of `ydoc['foo']`
input = <<'END'
tables:
- name: admin_users
columns:
- name: id
type: int
pkey: true
END
tree = Psych.parse(input)
visitor = MagicVisitor.create
ydoc = visitor.accept(tree)
p ydoc.tables[0].columns[0].name #=> "name"
p ydoc.tables[0].columns[0].type #=> "int"
This is necessary to generate custom object as mapping instead of Hash
according to context. For example:
TableObj = Struct.new('TableObj', 'name', 'columns')
ColumnObj = Struct.new('ColumnObj', 'name', 'type', 'pkey')
class CustomVisitor < Psych::Visitors::ToRuby
def initialize(*args)
super
@key_path = [] # ex: [] -> ['tables'] -> ['tables', 'columns']
end
def accept_key(k) # push keys
key = super k
@key_path << key
return key
end
def accept_value(v) # pop keys
value = super v
@key_path.pop()
return value
end
def empty_mapping(o) # generate custom object instead of Hash
case @key_path.last
when 'tables' ; return TableObj.new
when 'columns' ; return ColumnObj.new
else ; return super o
end
end
end
## example to generate custom object according to context
input = <<'END'
tables:
- name: admin_users
columns:
- name: id
type: int
pkey: true
END
tree = Psych.parse(input)
visitor = CustomVisitor.create
ydoc = visitor.accept(tree)
p ydoc['tables'][0].class #=> Struct::TableObj
p ydoc['tables'][0]['columns'][0].class #=> Struct::ColumnObj
This new class allows user to generate custom object instead of Hash. See document of CustomClassVisitor class for details.
|
I think I'm OK with the |
|
Thanks a lot.
I see. I'll revert the following commits.
And I'll leave the rest commits.
Is it OK? Give me your advice. |
|
@kwatch yes, that makes sense. Please do it! |
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(Redirected from https://bugs.ruby-lang.org/issues/12960?next_issue_id=12959 .)
New visitor class to create custom object intead of Hash.
It creates custom object according to context (= last mapping key).
ydoc.foo.barinstead ofydoc['foo']['bar'].ydoc['teams'][0].is_a?(Team)andydoc['teams'][0].members[0].is_a?(Member).See document of CustomClassVisitor class for details.
You may feel that CustomClassVisitor is very experimental. I hope that at least changes of 'to_ruby.rb' will be imported to upstream, because implementation of CustomClassVisitor requires monkey-pathing to 'to_ruby.rb'.