json_lib

Description:

json lib

Library made to simplify working with Json Data

intuitive API
no code generation
support for required and missing(optional) jason data
descriptive error reporting

Motivation #
This Library is useful when you:

are not interested in automatic code generated deserialization.
want better control when handling unexpected Json data.
want to read only parts of the Json data by path or by name.

APIs #
There are two 'flavors' of the api - freestanding functions and extensions on Map<String, dynamic> and List<dynamic>
Every json reading function has two variations:

'strict' - data expected to be present and not null. If data is missing function will throw an exception explaining the missing part.
'try' Prefixed - function will return null.

Every function has optional 'mapper' parameter that can be used to map retrieved value to expected data type.
There are two convenience functions asJsonMap(dynamic) and asJsonList(dynamic) that are used in combination with extension methods.
Usage #
For complete API and code examples please refer to json_lib_test and json_lib_test_extensions
Imports
import 'package:json_lib/json_lib.dart';
// Only if extension methods used
import 'package:json_lib/json_lib_extensions.dart';
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Property names and list indexes (freestanding functions)
final dynamic data = {'intField': 5, 'stringField': 'foo', 'doubleField': 2.3, 'nullField': null};
final dynamic dataList = <dynamic>[1, 'foo', 3];

final double someValue = jsonValue('doubleField', data); // 2.3
final double someValue = tryJsonValue('missing_filed', data); //null

final String val = jsonListItem(1, dataList); // 'foo'
final String val = tryJsonListItem(300, dataList); // null
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Property names and list indexes (extensions)
final jsonObject = asJsonMap(data);
final jsonList = asJsonList(dataList);

final double someValue = jsonObject.value('doubleField'); // 2.3
final double someValue = jsonObject.tryValue('missing_filed'); // null
final String val = jsonList.listItem(1); // 'foo'
final String val = jsonList.tryListItem(300); // null
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Using path
//sample data
final dynamic responseBody = [{
'name': 'Songs from a Room',
'genre': 'Folk',
'artist': {
'name': 'Leonard Cohen',
},
'tracks': [
{'name': 'Bird on the Wire', 'duration': 208},
{'name': 'Story of Isaac', 'duration': 218},
{'name': 'A Bunch of Lonesome Heroes', 'duration': 198},
]
}
];
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Freestanding functions
// this will throw exception if path is not found with description which part of the path is missing in the data
final int trackDuration = jsonPathValue([1, 'tracks', 0, 'duration'], responseBody); // 208
// this will not throw byt return nullable value
final int? trackDuration = tryJsonPathValue([1, 'tracks', 0, 'duration'], responseBody); // 208
final int? trackDuration = tryJsonPathValue([5, 'tracks', 0, 'duration'], responseBody); // null - index 5 is out of bounds
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Extensions
final jsonData = asList(responseBody);
// this will throw exception if path is not found with description which part of the path is missing in the data
final int trackDuration = jsonData.pathValue([1, 'tracks', 0, 'duration']); // 208
// this will not throw byt return nullable value
final int? trackDuration = jsonData.tryPathValue([1, 'tracks', 0, 'duration']); // 208
final int? trackDuration = jsonData.tryPathValue([5, 'tracks', 0, 'duration']); // null - index 5 is out of bounds
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Using mapper parameters
enum Genre { Rock, Jazz, Pop, Folk }

Genre? tryParseGenre(dynamic value) {
return Genre.values.firstWhereOrNull((e) => e.toString().toLowerCase() == 'genre.${value.toString().toLowerCase()}');
}

Genre genre = albumsJson.pathValue([0, 'genre'], tryParseGenre); // Genre.Folk
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Deserializing hierarchical data
static Album deserialize(dynamic data) {
final json = asJsonMap(data);
return Album(
name: json.value('name'),
artist: json.value('artist', Artist.deserialize),
tracks: json.valueList('tracks', Track.deserialize),
genre: json.value('genre', tryParseGenre),
);
}

static Artist deserialize(dynamic data) {
final json = asJsonMap(data);
return Artist(
name: json.value('name'),
founded: json.tryValue('founded'),
members: json.tryValueList('members') ?? [],
);
}

static Track deserialize(dynamic data) {
final json = asJsonMap(data);
return Track(
name: json.value('name'),
duration: json.tryValue('duration'),
);
}
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