flutter-view
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Flow control
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.
Pug
generated Dart
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.
Pug
generated Dart
app-bar
.title(as='title' null-if='user.name == null') ${user.name}
PlatformAppBar(
title: !(name == null) ?
Container(
child: Text(
'${name}',
),
) : null,
)
In the above example, the title of the AppBar widget will be set to null if the user.name is null.

slot

A slot is a placeholder for a value. It will take the value of the first valid child. Alternatively, you can also directly pass a value into it:
Pug
Generated Dart
wrapper(flutter-view :content[Widget])
slot(:value='content').content
.footer A footer
Column Wrapper({ required Widget content }) {
return Column(
children: __flatten([
content,
//-- FOOTER ----------------------------------------------------------
Container(
child: Text(
'A footer',
),
)
]),
);
}
Slot can function as an if/else. In the next example you see either the .status being shown, or the .empty.
Pug
generated Dart
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:
Pug
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.
Pug
generated Dart
tasks-page(flutter-view :tasks[List])
scaffold
slot(as='body')
.task(for='task in tasks')
.title ${task.title}
.description ${task.description}
Scaffold TasksPage({ required List tasks }) {
return Scaffold(
body:
//-- BODY ----------------------------------------------------------
Container(
child: (tasks as List).map((task) {
return
//-- TASK ----------------------------------------------------------
Container(
child: Column(
children: [
//-- TITLE ----------------------------------------------------------
Container(
child: Text(
'${task.title}',
),
),
//-- DESCRIPTION ----------------------------------------------------------
Container(
child: Text(
'${task.description}',
),
)
]),
),
);
}).toList(),
),
);
}
You can also get the index (starting at 0) of the current entry as such:
.task(for='task, index in tasks')
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