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nester
Flutter library to convert a list of widgets in a nested group of
widgets.
A beautifier plugin to easing your code syntax.
Features
- Ease the code syntax
- Can manage like a generic list
- Can manage like a queue
Installation
dependencies:
nester: ^1.2.1
import 'package:nester/nester.dart';
Example Usage
NESTER LIST
Will treated the as simple list. You are allowed to have just one
"next"
reference for each item in the list.
This is the most simple way to use Nester.
Recommended when you mostly have "one child" Widget inside your list.
Original code
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: const Text("Example"),
),
body: Padding(
padding: const EdgeInsets.all(20),
child: Container(
color: Colors.black12,
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[Text("Just a description")],
),
),
),
),
);
Using Nester
return Nester.list([
(next) => MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: next,
),
(next) => Scaffold(
appBar: AppBar(title: const Text("Example")),
body: next,
),
(next) => Padding(
padding: const EdgeInsets.all(20),
child: next,
),
(next) => Container(
color: Colors.black12,
child: next,
),
(next) => Center(child: next),
(_) => Column(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[Text("Just a text")],
),
]);
NOTE: The last next item in list will be always an empty
Container object. So is useless to pass it.
NESTER QUEUE
The Widget list will be treated like a queue.
Every "next" calling will consume the next item in the list.
This is useful when you using "multi-child" Widgets inside your list.
Original code
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: Scaffold(
appBar: AppBar(
title: const Text("Example"),
),
body: Padding(
padding: const EdgeInsets.all(50),
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: const [
Text("Left", textAlign: TextAlign.left),
Text("Center", textAlign: TextAlign.center),
Text("Right", textAlign: TextAlign.right),
],
),
),
),
);
Using Nester
return Nester.queue([
(next) => MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: next(),
),
(next) => Scaffold(
appBar: next() as PreferredSizeWidget,
body: next(),
),
(_) => AppBar(title: const Text("Example")),
(next) => Padding(
padding: const EdgeInsets.all(50),
child: next(),
),
(next) => Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: next(take: 3),
),
(_) => const Text("Left", textAlign: TextAlign.left),
(_) => const Text("Center", textAlign: TextAlign.center),
(_) => const Text("Right", textAlign: TextAlign.right),
]);
Skip and Take
The next({int skip, int take}) function accept two parameters.
- Param
skip will skip n calls on the queue list. Note that the
function wil NOT check for nested calling, just skip the next n items
inside the list. skip will be always applied before take.
- Param
take will consuming n items on the same level. If a item have a
nested calling will not count as consumed. The result will be an array of
Widgets.
Constraints
- if
skip and take are less than 0 will be considered 0
- if
skip is not null or 0 and take is null an empty Container
will be returned.
Throw Range Exception
The queue constructor accept throwRangeException (default:
false) to avoid the RangeError check.
If true every calling of next then exceed the list boundaries will
throw a RangeError exception.
When use take param the resulting array will not exceed the number of
remaining items in list.
When NOT use take and the next calling exceed the list bounds an
empty Container will be returned.
Deep in queue mode
Using of skip and take parameters could create confusion so
write some examples to explain better them behavior.
Suppose the have a variable trigger boolean to use to skip some items
inside a Column widget.
return Nester.queue([
...,
(next) => Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
next(skip: trigger ? 0: 2),
next(),
next(),
]),
(next) => Padding(..., child: next()),
(_) => const Text("If trigger true"),
(_) => const Text("Always show"),
(_) => const Text("Always show"),
]);
OR
return Nester.queue([
...,
(next) => Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: []
..addAll(next(skip: trigger ? 0: 2, take: trigger ? 1: 0))
..addAll(next(take: 2)),
),
(next) => Padding(..., child: next()),
(_) => const Text("If trigger true"),
(_) => const Text("Always show"),
(_) => const Text("Always show"),
]);
If trigger is true skip 0 and take 1.
If trigger is false skip 2 and take 0.
Why skip = 2?
Because skip will not go inside the tree to check the nested items.
Just skip the items on the raw list.
So need to skip the next Padding and Text (two items).
Instead take will consume all the item inside the tree. Take 1 it
mean consuming the next Padding then will consume the next Text
(two items).
Why addAll?
Because when you use take parameter the result will be always an
Array of Widgets, also if taking is 0 or 1.
NESTER EXTENDED
A extension of Queue.
Will be treated exactly like queue but extended it adding an extra
param in the next function than will allow to pass a dynamic value
to the next calling.
return Nester.extended([
(next, _) => MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: next(),
),
(next, _) => Scaffold(
appBar: next(param: "Example") as PreferredSizeWidget,
body: next(),
),
(_, title) => AppBar(title: Text(title)),
(next, _) => Padding(
padding: const EdgeInsets.all(50),
child: next(),
),
(next, _) => Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: next(take: 3, param: ["Left", "Center", "Right"]),
),
(_, param) => Text(param[0], textAlign: TextAlign.left),
(_, param) => Text(param[1], textAlign: TextAlign.center),
(_, param) => Text(param[2], textAlign: TextAlign.right),
]);
