Static Typing Hell

user_3293340 0
Viewed 73

My background is in Python where you treat everything as a duck, and free from defining types. I recently started coding in Dart, and here I am facing these type casting issues.

What's wrong with the below code?

The appendCsv function takes a List<List<dynamic>> parameter, getMarks function returns a List<dynamic> list.

I want to call the getMarks in a loop and append all the lists to another list e.g the x. And then pass that list to the appendCsv function.

List<List<dynamic>> x = [];
var v = await etea.getMarks('809', 70740) as Iterable<List<dynamic>>;
x.addAll(v);
print(x);
print(x.runtimeType);
// x = x as List<List<dynamic>>;
print(x.runtimeType);

appendCsv('802', x);

I am getting these kinds of mix errors.

type 'List<Iterable<String>>' is not a subtype of type 'Iterable<List<dynamic>>' in type cast

dart flutter
2 Answers

If getMarks returns a List< dynamic> you just have to add it to x.

List<List<dynamic>> x = [];
for(what ever){
    List<dynamic> v = await etea.getMarks('809', 70740);
    x.add(v);
}

or even

List<List<dynamic>> x = [];
for(what ever){
    x.add(await etea.getMarks('809', 70740));
}
user_129037020

Finally solved my issue, thanks to @AntEdote as well as @coolhack7's How to fix the error "'WhereIterable' is not a subtype of type 'List'"
The problem was in getMarks function it was returning a List<WhereIterable<String>> but I was treating it as List<dynamic>.
When you call .where on something, it returns a WhereIterable type, that's a stupid type name WhereIterable lol.
As described by coolhack7, I called .toList() on the WhereIterable<String> in getMarks and fixed the issue.

user_32933400
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