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Offline Programmer
Offline Programmer

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Flutter & Dart Tips - Week In Review

Hello Reader,

I am trying something new here. A "Week In Review" series where I share the Flutter\Dart tips I tweeted last week.

Let's try this...

1- You can iterate through a map in a null-safe manner using entries.


    for (var entry in items.entries) {
      //print the keys and values
      print('${entry.key}: ${entry.value}');
    }

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2- Lists can hold duplicate items. So If you want a collection of unique values, Use a Set instead.

In a Set, two elements cannot be equal, so the code below won’t compile.


    final citiesSet = {'Dublin', 'London', 'Paris', 'Dublin'};

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3- You can wait for the results of multiple Futures to complete using Future.wait


    class someAPI {
        Future<int> getThings() => Future.value(3000);
        Future<int> getItems() => Future.value(300);
        Future<int> getStuff() => Future.value(30);
    }

...

    final api = someAPI();
    final values = await Future.wait([
      api.getThings(),
      api.getItems(),
      api.getStuff(),
    ]);
    print(values);

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4- You can use GridView.count to create a grid that's two tiles wide in portrait mode and three tiles wide in landscape mode


    final Orientation orientation = MediaQuery.of(context).orientation;

...

    Flexible(
        child: GridView.count(
            crossAxisCount: (orientation == Orientation.portrait) ? 2 : 3,
            mainAxisSpacing: 4.0,
            crossAxisSpacing: 4.0,
            padding: const EdgeInsets.all(4.0),
            childAspectRatio:
                (orientation == Orientation.portrait) ? 1.0 : 1.3,
            children: someList
                .map(
                (catData) => aListItemWidget(catData),
                )
                .toList(),
        ),
    ),

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5- You can randomly select an item from a list using Random from dart:math


    import 'dart:math';

...

    int min = 0;
    int max = someList.length - 1;
    Random rnd = new Random();
    int r = min + rnd.nextInt(max - min);
    return someList[r];

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6- You can use the services library to lock the device orientation


    import 'package:flutter/services.dart';

...

    void main() async {
    await SystemChrome.setPreferredOrientations([
        DeviceOrientation.portraitUp,
    ]);

    runApp(App());
    }

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7- You can use the dart:io library to write a platform-specific code


    import 'dart:io' show Platform;

...

    if (Platform.isIOS) {
        doSomethingforIOS();
    }

    if (Platform.isAndroid) {
        doSomethingforAndroid();
    }

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8- You can turn any color to a Material Color


    const Map<int, Color> color = {
    50: Color.fromRGBO(255, 207, 68, .1),
    100: Color.fromRGBO(255, 207, 68, .2),
    200: Color.fromRGBO(255, 207, 68, .3),
    300: Color.fromRGBO(255, 207, 68, .4),
    400: Color.fromRGBO(255, 207, 68, .5),
    500: Color.fromRGBO(255, 207, 68, .6),
    600: Color.fromRGBO(255, 207, 68, .7),
    700: Color.fromRGBO(255, 207, 68, .8),
    800: Color.fromRGBO(255, 207, 68, .9),
    900: Color.fromRGBO(255, 207, 68, 1),
    };

    const MaterialColor custom_color =
        MaterialColor(0xFFFFCF44, color);

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See you next week. 👋🏻

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Cover image Immo Wegmann on Unsplash

Discussion (2)

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randalschwartz profile image
Randal L. Schwartz

Your duplicate set example compiles just fine. It just has a compile-time warning that can be easily ignored.

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offlineprogrammer profile image
Offline Programmer Author

Thanks, I'll check it out