• New mapValue for asMap*() and asJsonObject*() parses the values of a map, like the mapper of asList* does for the items of a list #73. An error inside a value reports the full location, like adidas.id.

  // {"nike": {"id": "421"}, "adidas": {"id": "532"}}
  Map<String, Shoe> shoes = pick(json).asJsonObjectOrEmpty(mapValue: Shoe.fromPick);
  

• New whenNullValue maps the entries with a null value, which mapValue ignores, like whenNull does for lists.

  Map<String, Shoe?> shoes = pick(json).asJsonObjectOrEmpty(
    mapValue: Shoe.fromPick,
    whenNullValue: (pick) => null,
  );
  

• New mapKey converts the keys. It receives a pick of the key, so the usual parsers work on it.

  // {"421": {"name": "Nike Zoom Fly 3"}}
  Map<int, Shoe> shoes = pick(json).asMapOrEmpty(
    mapKey: (key) => key.asIntOrThrow(),
    mapValue: Shoe.fromPick,
  );
  

  The keys of asJsonObject*() stay Strings, its mapKey can rename them. Use asMap*() to convert the keys to another type.

• All six parsers are affected: asMapOrThrow(), asMapOrEmpty(), asMapOrNull(), asJsonObjectOrThrow(), asJsonObjectOrEmpty() and asJsonObjectOrNull(). asJsonObject*() got two type parameters for it, a call without arguments still returns a Map<String, Object?>.

• New asPlainListOrThrow(), asPlainListOrEmpty() and asPlainListOrNull() return the items of a List as they are, without a mapper #74. Declare the item type to get a typed list, an item of another type throws a PickException that names it.

  List<Object?> items = pick(json, 'tags').asPlainListOrEmpty();
  List<String> tags = pick(json, 'tags').asPlainListOrEmpty();
  

• Better error messages #64, especially for absent values

  PickException: expected a non-null value at shoes[0].name, but it is absent
  
    query   shoes[0].name
                     ~~~~ no such key
    at      shoes[0] = {"id": 42, "size": "M"}
    hint    Use asStringOrNull() when the value may be null/absent at some point (String?).
  

  A value that can't be parsed is shown with its type, and large values are shortened.

  PickException: could not parse an int at shoes[0].size
  
    query   shoes[0].size
    found   "M"  (a String)
  

• New asJsonObjectOrThrow(), asJsonObjectOrEmpty() and asJsonObjectOrNull() return a Map<String, Object?> that goes straight into a fromJson function, no type arguments needed #70. Entries with a key that isn't a String are ignored.

• New asJsonObjectListOrThrow(), asJsonObjectListOrEmpty() and asJsonObjectListOrNull() for a list of JSON objects #70.

  // before
  pick(json, 'users').asListOrEmpty((pick) => pick.asMapOrThrow<String, dynamic>());
  // after
  pick(json, 'users').asJsonObjectListOrEmpty();
  

• New asMapListOrThrow<K, V>(), asMapListOrEmpty<K, V>() and asMapListOrNull<K, V>() for a list of maps with any key type #70.

• Fix Pick.isAbsent is true below a null, however the path is written #64. pick({'a': null}, 'a', 'b').isAbsent was false, while pick({'a': null}, 'a')('b').isAbsent was true.

• New PickException.fromPick(pick, 'expected a Timestamp') lets custom parsers throw errors like the built-in ones #64.

• New Pick.redactValues() masks error values while keeping keys and types visible; Pick.redactsValues exposes the policy to custom parsers and RequiredPick.redactValues() preserves non-null chaining #65.

• Fix as*OrThrow() and letOrThrow() no longer leave an internal _required_pick_error_hint entry in Pick.context. That also makes them as fast as their OrNull counterparts #68.

• Deprecated Pick.path, Pick.missingValueAtIndex, Pick.followablePath and Pick.debugParsingExit. The error message of a PickException shows where a pick failed. A custom parser that built its message from them throws PickException.fromPick(this, 'expected a Foo') instead #69.

• Allow .letOrNull((pick) => null) to return null without manually setting a nullable type #61
• CI 2024 update

• Remove long deprecated methods: addContext, asBool, asDateTime, asDouble, asInt, asList, asMap, asString. Use their as*OrThrow replacements.
• Add support for timezones in asDateTime* methods #47, #51
• Add official support for date formats RFC 3339, RFC 2822 and RFC 1036
• Push test coverage to 100% 🤘

• New: Support for more date formats. asDateTime* received an optional format parameter. By default, all possible formats will be parsed. To the existing ISO 8601 format, RFC 1123, RFC 850 and asctime have been added which are typically used for the HTTP header or cookies.
• Documentation added for asDouble and asMap

• New: pickFromJson(json, args...) allows parsing of a json String, without manually calling jsonDecode #41

• New: pickDeep(json, 'some.key.inside.the.object'.split('.')) allows picking with a dynamic depth #40

• Add Pick.index to get the element index for list items #38

  pick(["John", "Paul", "George", "Ringo"]).asListOrThrow((pick) {
    final index = pick.index!;
    return Artist(id: index, name: pick.asStringOrThrow());
  );
  

• Pick.asIntOrThrow() now allows parsing of doubles when one of the new roundDouble or truncateDouble parameters is true #37. Thx @stevendz

• Add dartdoc to asList*() extensions

• Deprecated parsing extensions of RequiredPick to acknowledge that all parsers eventually causes errors. From now on, always use .asIntOrThrow() instead of .required().asInt(). Only exception is .required().toString(). Read more in #34
• Replace dynamic with Object where possible
• Rename Pick.location() to Pick.debugParsingExit
• Removal of PickLocaiton and PickContext mixins. They are now part of Pick
• RequiredPick now extends Pick making it easier to write parsers for custom types

• Enable nullsafety (requires Dart >=2.12)

Backports 0.8.0 to pre-nullsafety

API changes #

• Remove long deprecated parseJsonTo* methods. Use the pick(json, args*) api

• New asXyzOrThrow() methods as shorthand for .required().asXyz() featuring better error messages

  • asBoolOrThrow()
  • asDateTimeOrThrow()
  • asDoubleOrThrow()
  • asIntOrThrow()
  • letOrThrow()
  • asListOrThrow()
  • asMapOrThrow()
  • asStringOrThrow()

• New Pick.isAbsent getter to check if a value is absent or null #24. Absent could mean

  1. Accessing a key which doesn't exist in a Map
  2. Reading the value from List when the index is greater than the length
  3. Trying to access a key in a Map but the found data a Object which isn't a Map

• New RequiredPick.nullable() converting a RequiredPick back to a Pick with potential null value

• New PickLocation.followablePath. While PickLocation.path contains the full path to the value, followablePath contains only the part which could be followed with a non-nullable value

• Breaking asList*() now requires the mapping function.

• Breaking asList*() now ignores null values when parsing. The map function now receives a RequiredPick as fist parameter instead of a Pick with a potential null value, making parsing easier.

  Therefore pick().required().asList((RequiredPick pick) => /*...*/) only maps non-nullable values. When your lists contain null it will be ignored. This is fine in most cases and simplifies the map function.

  In rare cases, where your lists contain null values with meaning, use the second parameter whenNull to map those null values .asList((pick) => Person.fromPick(pick), whenNull: (Pick it) => null). The function still receives a Pick which gives access to the context api or the PickLocation. But the Pick never holds any value.

Parsing changes #

• The String "true" and "false" are now parsed as boolean

• Breaking Don't parse doubles as int because the is no rounding method which satisfies all #31

• Breaking Allow parsing of "german" doubles with , as decimal separator #30

• Improve error messages with more details where parsing stopped

• Breaking asList*() methods now ignore null values. The map function now receives a RequiredPick as fist parameter instead of a Pick making parsing easier.

  Therefore pick().required().asList((RequiredPick pick) => /*...*/) only maps non-nullable values. When your lists contain null it will be ignored. This is fine in most cases and simplifies the map function.

  In rare cases, where your lists contain null values with meaning, use the second parameter whenNull to map those null values .asList((pick) => Person.fromPick(pick), whenNull: (Pick it) => null). The function still receives a Pick which gives access to the context api or the PickLocation. But the Pick never holds any value.

• Breaking Don't parse doubles as int because the is no rounding method which satisfies all #31

• Breaking Allow parsing of "german" doubles with , as decimal separator #30

• Improve error messages with more details where parsing stopped

• New RequiredPick.nullable() converting a RequiredPick back to a Pick with potential null value

• New PickLocation.followablePath. While PickLocation.path contains the full path to the value, followablePath contains only the part which could be followed with a non-nullable value

• New asXyzOrThrow() methods as shorthand for .required().asXyz() featuring better error messages
  • asBoolOrThrow()
  • asDateTimeOrThrow()
  • asDoubleOrThrow()
  • asIntOrThrow()
  • letOrThrow()
  • asListOrThrow()
  • asMapOrThrow()
  • asStringOrThrow()
• New Pick.isAbsent getter to check if a value is absent or null #24. Absent could mean
  1. Accessing a key which doesn't exist in a Map
  2. Reading the value from List when the index is greater than the length
  3. Trying to access a key in a Map but the found data a Object which isn't a Map
• The String "true" and "false" are now parsed as boolean
• More nnbd refactoring

• Migrate to nullsafety (required Dart >=2.12)
• Remove long deprecated parseJsonTo* methods. Use the pick(json, args*) api
• Improve dartdoc

• Rename Pick.addContext to Pick.withContext using deprecation
• Pick.fromContext now accepts 10 arguments for nested structures
• Fix Pick.fromContext always returning context not the value for key in context Map

• New context API. You can now attach relevant additional information for parsing directly to the Pick object. This allows passing information into fromPick constructors without adding new parameters to all constructors in between.

  // Add context
  final shoes = pick(json, 'shoes')
      .addContext('apiVersion', "2.3.0")
      .addContext('lang', "en-US")
      .asListOrEmpty((p) => Shoe.fromPick(p.required()));
  

  import 'package:version/version.dart';
  
  // Read context
  factory Shoe.fromPick(RequiredPick pick) {
    // read context API
    final version = pick.fromContext('newApi').required().let((pick) => Version(pick.asString()));
    return Shoe(
      id: pick('id').required().asString(),
      name: pick('name').required().asString(),
      // manufacturer is a required field in the new API
      manufacturer: version >= Version(2, 3, 0)
          ? pick('manufacturer').required().asString()
          : pick('manufacturer').asStringOrNull(),
      tags: pick('tags').asListOrEmpty(),
    );
  }
  

• Breaking: Pick and RequiredPick have chained their constructor signature. path is now a named argument and context has been added.

- RequiredPick(this.value, [this.path = const []])
+ RequiredPick(this.value, {this.path = const [], Map<String, dynamic> context})

• The path is now correctly forwarded after Pick#call or Pick#asListOrEmpty and always shows the full path since origin

• Fix error reporting for asMapOr[Empty|Null] and don't swallow parsing errors
• Throw Map cast errors when parsing, not lazily when accessing the data

• Fix error reporting of asListOrNull(mapToUser) and asListOrEmpty(mapToUser). Both now return errors during mapping and don't swallow them

• Print correct path in error message when json is null
• asDateTime() now skips parsing when the value is already a DateTime

Map objects #

New APIs to map picks to objects and to map list elements to objects.

RequiredPick.let<R>(R Function(RequiredPick pick) block): R
Pick.letOrNull<R>(R Function(RequiredPick pick) block): R

RequiredPick.asList<T>([T Function(Pick) map]): List<T> 
Pick.asListOrNull<T>([T Function(Pick) map]): List<T> 
Pick.asListOrEmpty<T>([T Function(Pick) map]): List<T> 

Here are two example how to actually use them.

// easily pick and map objects to dart objects
final Shoe oneShoe = pick(json, 'shoes', 0).letOrNull((p) => Shoe.fromPick(p));

// map list of picks to dart objects
final List<Shoe> shoes = 
     pick(json, 'shoes').asListOrEmpty((p) => Shoe.fromPick(p.required()));

Required picks #

Pick now offers a new required() method returning a RequiredPick. It makes sure the picked value exists or crashes if it is null. Because it can't be null, RequiredPick doesn't offer fallback methods like .asIntOrNull() but only .asInt(). This makes the API a bit easier to use for values you can't live without.

// use required() to crash if a object doesn't exist
final name = pick(json, 'shoes', 0, 'name').required().asString();
print(name); // Nike Zoom Fly 3

Note: Calling .asString() directly on Pick has been deprecated. You now have to call required() first to convert the Pick to a RequiredPick or use a mapping method with fallbacks.

Pick deeper #

Ever got a Pick/RequiredPick and you wanted to pick even further. This is now possible with the call method. Very useful in constructors when parsing methods.

  factory Shoe.fromPick(RequiredPick pick) {
    return Shoe(
      id: pick('id').required().asString(),
      name: pick('name').required().asString(),
      manufacturer: pick('manufacturer').asStringOrNull(),
      tags: pick('tags').asListOrEmpty(),
    );
  }

Bugfixes #

• Don't crash when selecting a out of range index from a List
• .asMap(), .asMapOrNull() and .asMapOrEmpty() now consistently return Map<dynamic, dynamic> (was Map<String, dynamic>)

Also the lib has been converted to use static extension methods which were introduced in Dart 2.6

asMap now expects the key type, defaults to dynamic instead of String

-Pick.asMap(): Map<String, dynamic>
+Pick.asMap<T>(): Map<T, dynamic>

New API! The old parse* methods are now deprecated, but still work. Replace them with the new pick(json, arg0-9...) method.

- final name = parseJsonToString(json, 'shoes', 0, 'name');
+ final name = pick(json, 'shoes', 0, 'name').asString();

pick returns a Pick which offers a rich API to parse values.

.asString()
.asStringOrNull()
.asMap()
.asMapOrEmpty()
.asMapOrNull()
.asList()
.asListOrEmpty()
.asListOrNull()
.asBool()
.asBoolOrNull()
.asBoolOrTrue()
.asBoolOrFalse()
.asInt()
.asIntOrNull()
.asDouble()
.asDoubleOrNull()
.asDateTime()
.asDateTimeOrNull()

• pubspec description updated

• Initial version