cv

Description:

cv

cv #
Content Values map helpers.
These helpers are about mapping map fields to named fields and vice versa. Key features:

Object to Map conversion
Map to Object conversion
No code generation
All objects are mutable
Deals with null and undefined values
Field type is final and strongly enforced
All fields have final key and mutable values

Drawbacks:

A field value must be access through a getter (value or v)

Usage #
A model can define by defining fields in the following way:
import 'package:cv/cv.dart';

class Note extends CvModelBase {
final title = CvField<String>('title');
final content = CvField<String>('content');
final date = CvField<DateTime>('date');

@override
/// List of the fields of the model
List<CvField> get fields => [title, content, date];
}
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You can convert the object to a map:
var note = Note()
..title.v = 'My note'
..content.v = 'My note context'
..date.v = DateTime(2021, 08, 16);
expect(note.toMap(), {
'title': 'My note',
'content': 'My note context',
'date': DateTime(2021, 08, 16)
});
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and from a map:
var note = Note();
note.fromMap({
'title': 'My note',
'content': 'My note context',
'date': DateTime(2021, 08, 16)
});
expect(note.title.v, 'My note');
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For convenience, extension on Map are created to simply call .cv<Type>() on map to convert them to object:
// Add the builder once (requires dart 2.15 - use cvAddBuilder otherwise)
cvAddConstructor(Note.new);

// Any map can be converted to a note object
var note = {'title': 'My note'}.cv<Note>();
expect(note.title.v, 'My note');
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Complex object examples #
Inner object #
Here is a small example of an object containing other object
class Rect extends CvModelBase {
final point = CvModelField<Point>('point');
final size = CvModelField<Size>('size');

@override
List<CvField> get fields => [point, size];
}

class Point extends CvModelBase {
final x = CvField<int>('x');
final y = CvField<int>('y');

@override
List<CvField> get fields => [x, y];
}

class Size extends CvModelBase {
final width = CvField<int>('width');
final height = CvField<int>('height');

@override
List<CvField> get fields => [width, height];
}
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// Add the builders once
cvAddConstructor(Rect.new);
cvAddConstructor(Point.new);
cvAddConstructor(Size.new);
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// Any map can be converted to a rect object
var rect = {
'point': {'x': 100, 'y': 50},
'size': {'width': 300, 'height': 200}
}.cv<Rect>();
var size = rect.size.v!;
expect(size.width.v, 300);

// and you can convert your object to a map
print(rect.toMap());
// {point: {x: 100, y: 50}, size: {width: 300, height: 200}}
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Inner object list #
class ShoppingCart extends CvModelBase {
final items = CvModelListField<Item>('items');

@override
List<CvField> get fields => [items];
}

class Item extends CvModelBase {
final name = CvField<String>('name');
final price = CvField<int>('price');

@override
List<CvField> get fields => [name, price];
}
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// Add the builders once
cvAddConstructor(Cart.new);
cvAddConstructor(Item.new);
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// Any map can be converted to a cart object
var cart = {
'items': [
{'name': 'Chair', 'price': 50},
{'name': 'Lamp', 'price': 12}
]
}.cv<ShoppingCart>();
var items = cart.items.v!;
expect(items[0].name.v, 'Chair');

print(cart.toMap());
// {items: [{name: Chair, price: 50}, {name: Lamp, price: 12}]}
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Json #
Additional json helpers extension on string are available if you include:
import 'package:cv/cv_json.dart';
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Using .cv() you can decode a single object:
var cartJson =
'{"items":[{"name":"Chair","price":50},{"name":"Lamp","price":12}]}';

// Create a cart object
var cart = cartJson.cv<ShoppingCart>();
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Using .cvList(), a list of object:
var itemsJson =
'[{"name":"Chair","price":50},{"name":"Lamp","price":12}]';

/// Create a list of objects
var items = itemsJson.cvList<Item>();
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and you can encode to json both lists and objects using toJson():
print(cart.toJson());
// {items: [{name: Chair, price: 50}, {name: Lamp, price: 12}]}

print(items.toJson());
// [{"name":"Chair","price":50},{"name":"Lamp","price":12}]
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Why #

Relying on code generator always adds a level of build complexity (and build failure risk).
No setup needed other than adding the package
Having mutable values can lead to more mistakes though. But well, you know what your are doing and it is convenient
In Java, I used to like ContentValues in Android, having a little more control than a regular HashMap.
In Java, I also used to like Gson for its simplicity: just define a class.

Git setup #
Usage #
In your pubspec.yaml:
dependencies:
cv:
git:
url: https://github.com/tekartik/cv.dart
ref: dart3a
path: packages/cv
version: '>=0.1.0'
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