Module: Scrimp::JsonThrift

Defined in:
lib/scrimp/json_thrift.rb

Overview

Generated Thrift struct classes can extend this module to gain a #from_hash method that will build them from a hash representation. The hash representation uses only types that can be readily converted to/from json. See the README’s “JSON Representation” section.

Instance Method Summary collapse

Instance Method Details

#from_hash(hash) ⇒ Thrift::Struct

Construct a new instance of the class extending this module and populate its fields with values from a hash.

Parameters:

  • hash (Hash) —

    populates fields of the Thrift struct that have names that match its keys (string keys only)

Returns:

  • (Thrift::Struct)

Raises:

  • (Thrift::TypeError) —

    if one of the values in hash is not a valid type for its field or a field exists with an invalid type



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# File 'lib/scrimp/json_thrift.rb', line 12

def from_hash(hash)
  thrift_struct = self.new

  hash.each do |(k, v)|
    field = thrift_struct.struct_fields.find {|sk,sv| sv[:name] == k}.last
    value = json_type_to_thrift_type(v, field)
    Thrift.check_type(value, field, field[:name]) # raises Thrift::TypeError if value is the wrong type
    thrift_struct.send("#{field[:name]}=", value)
  end

  thrift_struct
end

#json_type_to_thrift_type(value, field) ⇒ Object

Converts value to a Thrift type that can be passed to a Thrift setter for the given field.

Parameters:

  • value (Object) —

    the parsed json type to be converted

  • field (Hash) —

    the Thrift field that will accept value

Returns:

  • (Object) —

    value converted to a type that the setter for field will expect

Raises:

  • (Thrift::TypeError) —

    if field has an invalid type



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# File 'lib/scrimp/json_thrift.rb', line 31

def json_type_to_thrift_type(value, field)
  type = Thrift.type_name(field[:type])
  raise Thrift::TypeError.new("Type for #{field.inspect} not found.") unless type
  type.sub!('Types::', '')
  v = value
  if type == 'STRUCT'
    v = field[:class].from_hash(v)
  elsif [Thrift::Types::LIST, Thrift::Types::MAP, Thrift::Types::SET].include? field[:type]
    if type == 'MAP'
      # JSON doesn't allow arbitrary keys in objects, so maps will be represented
      # by a vector of key-value pairs
      v = {}
      value.each do |(key, value)|
        thrift_key = json_type_to_thrift_type(key, field[:key])
        thrift_value = json_type_to_thrift_type(value, field[:value])
        v[thrift_key] = thrift_value
      end
    else
      v = value.collect{|e| json_type_to_thrift_type(e, field[:element])}
      v = Set.new(v) if type == 'SET'
    end
  elsif type == 'DOUBLE'
    v = v.to_f
  elsif field[:enum_class] && value.to_i != value
    v = field[:enum_class].const_get('VALUE_MAP').invert[value] || value
  # TODO: STOP, VOID, BYTE
  end
  v
end