I want to show and hide HomeCategory objects based on a bool. I have this in place currently:
_isOn ? HomeCategory(0, Icons.check, Colors.blue[800], "Check In", [Task(0, "Check In", true),]) : "",
However it throws an error because I am passing an empty string if its turned off. How can I pass it an empty object or hide it? It is a list like so:
_isOn ? HomeCategory(0, Icons.check, Colors.blue[800], "Check In", [Task(0, "Check In", true),]) : "",
HomeCategory(1, Icons.chat_bubble, Colors.red, "Forums", [ Task(1, "Questions", true),]),
HomeCategory(2, Icons.star, Colors.blue[200], "Goals", [ Task(2, "Goals", true),]),
HomeCategory(3, Icons.monetization_on, Colors.orange[700], "Budget", [ Task(3, "Budget", true),]),
HomeCategory(4, Icons.shopping_basket, Colors.brown[300], "Shopping", [ Task(4, "Items", true),]),
HomeCategory(5, Icons.calendar_today, Colors.purple[900], "My Day & Calendar", [ Task(4, "Events", false),]),
HomeCategory(6, Icons.check_circle_outline, Colors.teal[700], "Check Out", [ Task(4, "Tasks", false),]),
HomeCategory(7, Icons.dock, Colors.grey[700], "Connect", [ Task(4, "Tasks", false),]),
HomeCategory(8, Icons.local_pharmacy, Colors.green, "My Medication", [ Task(4, "Tasks", false),]),
HomeCategory(9, Icons.settings, Colors.yellow[800], "Settings", [ Task(4, "Tasks", false),]),
4 Answers
You can do this :
_isOn ? HomeCategory() : SizedBox()
But since it is in a List<Widget>, an if condition is cleaner :
if(_isOn)
HomeCategory()
You don't need to use ternary operators at all. Ever since Dart 2.3, you can use control statements in collections (i.e. lists and maps) to add things conditionally or in a loop. In your case, you would want to use the conditional syntax:
Column( // as an example
children: [
if (isOn0) HomeCategory(0, Icons.check, Colors.blue[800], "Check In", [Task(0, "Check In", true),]),
if (isOn1) HomeCategory(1, Icons.chat_bubble, Colors.red, "Forums", [ Task(1, "Questions", true),]),
if (isOn2) HomeCategory(2, Icons.star, Colors.blue[200], "Goals", [ Task(2, "Goals", true),]),
...
],
),
You could make this even cleaner by combining it with the loop syntax:
Column(
children: [
for (var category in categories)
if (category.isOn)
HomeCategory(
category.id,
category.icon,
category.color,
category.message,
category.tasks,
),
],
),
EDIT: If you absolutely must have an explicit incrementing index for each HomeCategory widget, you can do it like this:
Conditional-Only Syntax:
int categoryIdx = 0; // declare at the top of the build method
...
Column( // as an example
children: [
if (isOn0) HomeCategory(categoryIdx++, Icons.check, Colors.blue[800], "Check In", [Task(0, "Check In", true),]),
if (isOn1) HomeCategory(categoryIdx++, Icons.chat_bubble, Colors.red, "Forums", [ Task(1, "Questions", true),]),
if (isOn2) HomeCategory(categoryIdx++, Icons.star, Colors.blue[200], "Goals", [ Task(2, "Goals", true),]),
...
],
),
Conditional + Loop Syntax:
int categoryIdx = 0; // declare at the top of the build method
...
Column(
children: [
for (var category in categories)
if (category.isOn)
HomeCategory(
categoryIdx++,
category.icon,
category.color,
category.message,
category.tasks,
),
],
),
I am utils so:
children: [
if (_selectedIndex == 0) ...[
DayScreen(),
] else if(_selectedIndex == 1)...[
StatsScreen(),
],
],
If you want to use ternary operator to handle widgets, then in else you can put Container(), or Sizedbox() widget.
condition ? HomeCategory("Check In") : Container()
I use container or sizedbox widget everytime, when I dont have anything for else condition, so I pass Container(), as it doesn't occupy any space, or render any style
