In your views you often want to only conditionally show something, or loop through a list of items. For this flutter-view has some intentionally simple flow control keywords.
if
This will only render the widget if the passed condition is true.
user-profile(flutter-view :user[User])
.user
.name ${user.name}
.company(if='user.company != null') Works at ${user.company}
UserProfile({required User user}) {
return Container(
child: Column(
children: [
Container(
child: Text('${user.name}'),
),
user.company != null ?
Container(
child: Text('Works at ${user.company}'),
)
: SizedBox(),
],
),
);
}
// left out some flatten operations for simplicity
In the above example, the company will only be shown if the passed user has the company property set.
if-null
This will only render the widget if the passed condition is false, otherwise it returns null.
With type and null-safety in Dart, you sometimes need to either pass an argument or null. The normal if above will return a SizedBox() if the condition fails. For building widget trees, this is usually makes sense. However sometimes we need to pass an argument that can be null, depending on a condition. In these edge cases, use if-null.
Slot can function as an if/else. In the next example you see either the .status being shown, or the .empty.
tasks-page(flutter-view :tasks[List])
scaffold
slot(as='body')
.status(if='tasks.isNotEmpty') You have ${tasks.length} tasks
.empty You have no tasks yet...
Scaffold TasksPage({ required List tasks }) {
return Scaffold(
body: (tasks.isNotEmpty) ?
//-- STATUS ----------------------------------------------------------
Container(
child: Text(
'You have ${tasks.length} tasks',
),
):
true ?
//-- EMPTY ----------------------------------------------------------
Container(
child: Text(
'You have no tasks yet...',
),
)
: Container(),
);
}
As you can see in the above example, you can use the as property to assign the slot value to a parameter as well. In this case, the content of the slot is placed in the body parameter of the Scaffold.
By adding multiple children with if to a slot, you can also create a switch/case:
slot
.apple(if='fruit=="Apple"')
.pear(if='fruit=="Pear"')
.peach(if='fruit=="Peach"')
.unknown // the fallback
for
Use for to repeat a widget for every value in a list. For every repetition, the value gets assigned to a variable, which you can use to render the widget and its children.
