CODEWITHSUNDEEP
listdictionaryflutter
Chen Li Yong
Chen Li Yong

Reputation: 6107

Can anyone create/add a simple "map indexed" method on List on Flutter?

Based on some answers on Stack Overflow, I tried to create an "extension" of List for mapIndexed, that is, a map function which also passes index. This is what I got:

mixin MapIndexed on List {

  Iterable<U> mapIndexed<T, U>(U Function(T e, int i) f) {
    int i = 0;
    return map<U>((it) { final t = i; i++; return f(it, t); });
  }

}

The problem is, I don't know how to call this. I created this based on the iOS Swift's extension concept. Ultimately, I just want that I can call result = myList.mapIndexed((element, index) => doMapping);. How can I do this correctly? The way it is right now, the closest I can do to achieve this is by function:

Iterable<U> mapIndexed<T, U>(List<T> list, U Function(T e, int i) f) {
  int i = 0;
  return list.map<U>((it) { final t = i; i++; return f(it, t); });
}

result = mapIndexed(list, (element, index) => doMapping);

Upvotes: 0

Views: 334

Answers (1)

pskink
pskink

Reputation: 24740

try the following:

extension MapIndexed on Iterable {
    Iterable<U> mapIndexed<T, U>(U Function(T e, int i) f) {
    int i = 0;
    return map<U>((it) { final t = i; i++; return f(it, t); });
  }
}

with that you could test it by: 

print([1,3,5].mapIndexed((value, index) => index * 10 + value));

you should see the output:

(1, 13, 25)

Upvotes: 2

Related Questions