class JSON::PullParser

• JSON::PullParser
• Reference
• Object

Overview

This class allows you to consume JSON on demand, token by token.

Each read_* method consumes the next token. Sometimes it consumes only one token (like #read_begin_array), sometimes it consumes a full valid value (like #read_array).

You must be careful when calling those methods, as they move forward into the JSON input you are pulling. Calling #read_string twice will return the next two strings (if possible), not twice the same.

If you try to read a token which is not the one currently under the cursor location, an exception ParseException will be raised.

Example:

input = %(
  {
    "type": "event",
    "values": [1, 4, "three", 10]
  }
)
pull = JSON::PullParser.new(input)
pull.read_begin_object
pull.read_object_key # => "type"
pull.read_string     # => "event"
# Actually you can also use `read_string` to read a key
pull.read_string # => "values"
pull.read_begin_array
pull.read_int    # => 1
pull.read_int    # => 4
pull.read_string # => "three"
pull.read_int    # => 10
pull.read_end_array
pull.read_end_object

Another example reading the same object:

pull = JSON::PullParser.new(input)
pull.read_object do |key|
  case key
  when "type"
    pull.read_string # => "event"
  when "values"
    pull.read_array do
      if v = pull.read?(Int8)
        v
      else
        pull.read_string
      end
    end
  end
end

This example fails:

pull = JSON::PullParser.new(input)
pull.read_begin_object
pull.read_object_key # => "type"
pull.read_string     # => "event"
pull.read_end_object # => raise an exception. The current token is a string ("values"), not the end of an object.

Defined in:

Constructors

• .new(input)

  Creates a PullParser which will consume the JSON input.

Instance Method Summary

• #bool_value : Bool
• #column_number

  Returns the current column number.

• #float_value : Float64
• #int_value : Int64
• #kind : Kind
• #line_number

  Returns the current line number.

• #location : Tuple(Int32, Int32)

  Returns the current location.

• #max_nesting : Int32
• #max_nesting=(max_nesting : Int32)
• #on_key(key, & : self -> _)

  Reads an object keys and yield when key is found.

• #on_key!(key, & : self -> _)

  Reads an object keys and yield when key is found.

• #raise(message : String) : NoReturn

  Raises ParseException with message at current location.

• #raw_value : String
• #read?(klass : Bool.class) : Bool | Nil

  Reads a Bool value and returns it.

• #read?(klass : Int128.class) : Int128 | Nil

  Reads an Int128 value and returns it.

• #read?(klass : Int16.class) : Int16 | Nil

  Reads an Int16 value and returns it.

• #read?(klass : Int32.class) : Int32 | Nil

  Reads an Int32 value and returns it.

• #read?(klass : Int64.class) : Int64 | Nil

  Reads an Int64 value and returns it.

• #read?(klass : Int8.class) : Int8 | Nil

  Reads an Int8 value and returns it.

• #read?(klass : UInt128.class) : UInt128 | Nil

  Reads an UInt128 value and returns it.

• #read?(klass : UInt16.class) : UInt16 | Nil

  Reads an UInt16 value and returns it.

• #read?(klass : UInt32.class) : UInt32 | Nil

  Reads an UInt32 value and returns it.

• #read?(klass : UInt64.class) : UInt64 | Nil

  Reads an UInt64 value and returns it.

• #read?(klass : UInt8.class) : UInt8 | Nil

  Reads an UInt8 value and returns it.

• #read?(klass : Float32.class) : Float32 | Nil

  Reads an Float32 value and returns it.

• #read?(klass : Float64.class) : Float64 | Nil

  Reads an Float64 value and returns it.

• #read?(klass : String.class) : String | Nil

  Reads a String value and returns it.

• #read_array(&)

  Reads a whole array.

• #read_array_or_null(&)

  Reads an array or a null value, and returns it.

• #read_begin_array

  Reads the beginning of an array.

• #read_begin_object

  Reads the beginning of an object.

• #read_bool : Bool

  Reads a Bool value.

• #read_bool_or_null : Bool | Nil

  Reads a Bool or a null value, and returns it.

• #read_end_array

  Reads the end of an array.

• #read_end_object

  Reads the end of an object.

• #read_float : Float64

  Reads a float value.

• #read_float_or_null : Float64 | Nil

  Reads a float or a null value, and returns it.

• #read_int : Int64

  Reads an integer value.

• #read_int_or_null : Int64 | Nil

  Reads an integer or a null value, and returns it.

• #read_next : Kind

  Reads the next lexer's token.

• #read_null : Nil

  Reads a null value and returns it.

• #read_null? : Bool

  Reads the current token if its value is null.

• #read_null_or(&)

  Reads a null value and returns it, or executes the given block if the value is not null.

• #read_object(&)

  Reads a whole object.

• #read_object_key : String

  Reads an object's key and returns it.

• #read_object_or_null(&)

  Reads an object or a null value, and returns it.

• #read_raw(json) : Nil

  Reads the new value and fill the a JSON builder with it.

• #read_raw : String

  Read the next value and returns it.

• #read_string : String

  Reads a string and returns it.

• #read_string_or_null : String | Nil

  Reads a string or a null value, and returns it.

• #skip : Nil

  Skips the next value.

• #string_value : String

Constructor Detail

Instance Method Detail

pull = JSON::PullParser.new %([null, true, 1, "foo", [1, "two"], {"foo": "bar"}])
pull.read_begin_array
pull.read_raw # => "null"
pull.read_raw # => "true"
pull.read_raw # => "1"
pull.read_raw # => "\"foo\""
pull.read_raw # => "[1,\"two\"]"
pull.read_raw # => "{\"foo\":\"bar\"}"
pull.read_end_array