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from_json.cr
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from_json.cr
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# Deserializes the given JSON in *string_or_io* into
# an instance of `self`. This simply creates a `parser = JSON::PullParser`
# and invokes `new(parser)`: classes that want to provide JSON
# deserialization must provide an `def initialize(parser : JSON::PullParser)`
# method.
#
# ```
# Int32.from_json("1") # => 1
# Array(Int32).from_json("[1, 2, 3]") # => [1, 2, 3]
# ```
def Object.from_json(string_or_io) : self
parser = JSON::PullParser.new(string_or_io)
new parser
end
# Deserializes the given JSON in *string_or_io* into
# an instance of `self`, assuming the JSON consists
# of an JSON object with key *root*, and whose value is
# the value to deserialize.
#
# ```
# Int32.from_json(%({"main": 1}), root: "main") # => 1
# ```
def Object.from_json(string_or_io, root : String) : self
parser = JSON::PullParser.new(string_or_io)
parser.on_key!(root) do
new parser
end
end
# Parses a `String` or `IO` denoting a JSON array, yielding
# each of its elements to the given block. This is useful
# for decoding an array and processing its elements without
# creating an Array in memory, which might be expensive.
#
# ```
# require "json"
#
# Array(Int32).from_json("[1, 2, 3]") do |element|
# puts element
# end
# ```
#
# Output:
#
# ```text
# 1
# 2
# 3
# ```
#
# To parse and get an `Array`, use the block-less overload.
def Array.from_json(string_or_io) : Nil
parser = JSON::PullParser.new(string_or_io)
new(parser) do |element|
yield element
end
nil
end
def Nil.new(pull : JSON::PullParser)
pull.read_null
end
def Bool.new(pull : JSON::PullParser)
pull.read_bool
end
{% for type, method in {
"Int8" => "i8",
"Int16" => "i16",
"Int32" => "i32",
"Int64" => "i64",
"UInt8" => "u8",
"UInt16" => "u16",
"UInt32" => "u32",
"UInt64" => "u64",
} %}
def {{type.id}}.new(pull : JSON::PullParser)
{{type.id}}.new!(pull.read_int)
end
def {{type.id}}.from_json_object_key?(key : String)
key.to_{{method.id}}?
end
{% end %}
def Float32.new(pull : JSON::PullParser)
case pull.kind
when .int?
value = pull.int_value.to_f32
pull.read_next
value
else
pull.read_float.to_f32
end
end
def Float32.from_json_object_key?(key : String)
key.to_f32?
end
def Float64.new(pull : JSON::PullParser)
case pull.kind
when .int?
value = pull.int_value.to_f
pull.read_next
value
else
pull.read_float.to_f
end
end
def Float64.from_json_object_key?(key : String)
key.to_f64?
end
def String.new(pull : JSON::PullParser)
pull.read_string
end
def String.from_json_object_key?(key : String)
key
end
def Array.new(pull : JSON::PullParser)
ary = new
new(pull) do |element|
ary << element
end
ary
end
def Array.new(pull : JSON::PullParser)
pull.read_array do
yield T.new(pull)
end
end
def Set.new(pull : JSON::PullParser)
set = new
pull.read_array do
set << T.new(pull)
end
set
end
# Reads a Hash from the given pull parser.
#
# Keys are read by invoking `from_json_object_key?` on this hash's
# key type (`K`), which must return a value of type `K` or `nil`.
# If `nil` is returned a `JSON::ParseException` is raised.
#
# Values are parsed using the regular `new(pull : JSON::PullParser)` method.
def Hash.new(pull : JSON::PullParser)
hash = new
pull.read_object do |key, key_location|
parsed_key = K.from_json_object_key?(key)
unless parsed_key
raise JSON::ParseException.new("Can't convert #{key.inspect} into #{K}", *key_location)
end
hash[parsed_key] = V.new(pull)
end
hash
end
def Tuple.new(pull : JSON::PullParser)
{% begin %}
pull.read_begin_array
value = Tuple.new(
{% for i in 0...T.size %}
(self[{{i}}].new(pull)),
{% end %}
)
pull.read_end_array
value
{% end %}
end
def NamedTuple.new(pull : JSON::PullParser)
{% begin %}
{% for key in T.keys %}
%var{key.id} = nil
%found{key.id} = false
{% end %}
location = pull.location
pull.read_object do |key|
case key
{% for key, type in T %}
when {{key.stringify}}
%var{key.id} = {{type}}.new(pull)
%found{key.id} = true
{% end %}
else
pull.skip
end
end
{% for key, type in T %}
if %var{key.id}.nil? && !%found{key.id} && !{{type.nilable?}}
raise JSON::ParseException.new("Missing json attribute: {{key}}", *location)
end
{% end %}
{
{% for key, type in T %}
{{key}}: (%var{key.id}).as({{type}}),
{% end %}
}
{% end %}
end
def Enum.new(pull : JSON::PullParser)
case pull.kind
when .int?
from_value(pull.read_int)
when .string?
parse(pull.read_string)
else
raise "Expecting int or string in JSON for #{self.class}, not #{pull.kind}"
end
end
def Union.new(pull : JSON::PullParser)
location = pull.location
# Optimization: use fast path for primitive types
{% begin %}
# Here we store types that are not primitive types
{% non_primitives = [] of Nil %}
{% for type, index in T %}
{% if type == Nil %}
return pull.read_null if pull.kind.null?
{% elsif type == Bool ||
type == Int8 || type == Int16 || type == Int32 || type == Int64 ||
type == UInt8 || type == UInt16 || type == UInt32 || type == UInt64 ||
type == Float32 || type == Float64 ||
type == String %}
value = pull.read?({{type}})
return value unless value.nil?
{% else %}
{% non_primitives << type %}
{% end %}
{% end %}
# If after traversing all the types we are left with just one
# non-primitive type, we can parse it directly (no need to use `read_raw`)
{% if non_primitives.size == 1 %}
return {{non_primitives[0]}}.new(pull)
{% end %}
{% end %}
string = pull.read_raw
{% for type in T %}
begin
return {{type}}.from_json(string)
rescue JSON::ParseException
# Ignore
end
{% end %}
raise JSON::ParseException.new("Couldn't parse #{self} from #{string}", *location)
end
# Reads a string from JSON parser as a time formated according to [RFC 3339](https://tools.ietf.org/html/rfc3339)
# or other variations of [ISO 8601](http://xml.coverpages.org/ISO-FDIS-8601.pdf).
#
# The JSON format itself does not specify a time data type, this method just
# assumes that a string holding a ISO 8601 time format can be interpreted as a
# time value.
#
# See `#to_json` for reference.
def Time.new(pull : JSON::PullParser)
Time::Format::ISO_8601_DATE_TIME.parse(pull.read_string)
end
struct Time::Format
def from_json(pull : JSON::PullParser)
string = pull.read_string
parse(string, Time::Location::UTC)
end
end
module JSON::ArrayConverter(Converter)
def self.from_json(pull : JSON::PullParser)
ary = Array(typeof(Converter.from_json(pull))).new
pull.read_array do
ary << Converter.from_json(pull)
end
ary
end
end
module JSON::HashValueConverter(Converter)
def self.from_json(pull : JSON::PullParser)
hash = Hash(String, typeof(Converter.from_json(pull))).new
pull.read_object do |key, key_location|
parsed_key = String.from_json_object_key?(key)
unless parsed_key
raise JSON::ParseException.new("Can't convert #{key.inspect} into String", *key_location)
end
hash[parsed_key] = Converter.from_json(pull)
end
hash
end
end
module Time::EpochConverter
def self.from_json(value : JSON::PullParser) : Time
Time.unix(value.read_int)
end
end
module Time::EpochMillisConverter
def self.from_json(value : JSON::PullParser) : Time
Time.unix_ms(value.read_int)
end
end
module String::RawConverter
def self.from_json(value : JSON::PullParser)
value.read_raw
end
end