Question 227500 in Flutter Question posted in
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Flutter – How do I check if a List of Maps does *not* contain a specific key in Dart?

How do I check if a List of Maps List<Map<String, List<CustomObject>>> listOfMaps does not contain a specific key?

I am looping through listOfMaps and checking if a map contains a specific key.

If so I write over the values (code below):

listOfMaps.forEach((map) {
      if (map.containsKey(key)) {
        // write over values...
      }
    });

However if the listOfMaps does not contain the key I want to add the new map to the list:

listOfMaps.add(
        {key: [
      // Custom Objects
    ]}
    );

How do I check if listOfMaps does not contain a specific key?

*Edit:

listOfMaps = [
{'map1': [listOfCustomObjects]},
{'map2': [listOfCustomObjects]},
{'map3': [listOfCustomObjects]},
]

I am now dealing with new data:
{'map4': [listOfCustomObjects]}

if listOfMaps doesn’t contain key ‘map4’ I want to add a map, if listOfMaps does contain ‘map4’ already I want to write over the values.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    A solution that I came up with... If anybody has a simpler way of doing it let me know...

      checkIfListOfMapsContainsKey({
    required String key,
    required List<Map<String, List<CustomObject>>> listOfMaps,
  }) {
    bool hasKey = false;
    listOfMaps.forEach((map) {
      if (map.containsKey(key)) {
        hasKey = true;
      }
    });
    return hasKey;
  }

    then:

    bool hasKey = checkIfListOfMapsContainsKey(
          key: key,
          listOfMaps: listOfMaps,
        );
        if (hasKey == false) {
          listOfMaps.add({'map4': [listOfObjects]});
          
        }

  2. 0

    Simple enough.

    listOfMaps.update('map4', (old) => (old with new), ifAbsent: () => new);

    EDIT: ooops. That’s not the problem to be solved. I’ll just leave this here because people forget this works for some problems. {sigh}

    I’d also suggest that the ordering of the maps is likely insignificant, so this should really just be a map with keys, not a list of maps with a single key, and then my solution is applicable.

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