15

In the following code, I'm getting inspection warning with 'prefer const literals as parameters of constructors on @immutable classes' and it's annoying. What should I do to make it go away?

screenshot from ide

Container(
        margin: const EdgeInsets.all(20),
        width: double.infinity,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            TextField(
              decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter a search term'),
            ),
            Text("these are the search results", textAlign: TextAlign.left),
          ],
        ),
      )

I have tried to make every constructor call 'const' with no avail.

Container(
        margin: const EdgeInsets.all(20),
        width: double.infinity,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const TextField(
              decoration: const InputDecoration(
                  border: const OutlineInputBorder(),
                  hintText: 'Enter a search term'),
            ),
            const Text("these are the search results", textAlign: TextAlign.left),
          ],
        ),
      ),
Shawn McCool
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1 Answers1

45

Just mark the list as const:

Container(
    margin: const EdgeInsets.all(20),
    width: double.infinity,
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: const [
        TextField(
          decoration: InputDecoration(
              border: OutlineInputBorder(),
              hintText: 'Enter a search term'),
        ),
        Text("these are the search results", textAlign: TextAlign.left),
      ],
    ),
  ),
mmcdon20
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    Why should define the list as Constant? – Davoud Nov 25 '21 at 03:55
  • 5
    By making the list `const` the list and everything within the list will become compile-time constants. This can only be done if everything inside the list is able to be `const`. The benefit is that the list will only be created once at compile time rather than every time the surrounding `build` method is called. – mmcdon20 Nov 25 '21 at 04:08