nester

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

• Add the dependency

dependencies:
  nester: ^1.2.1

• Import the package

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), // or [ next(), next(), next() ],
          ),
      (_) => 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),
    ]);