CODEWITHSUNDEEP
flutterdartlowercase
fay
fay

Reputation: 41

How to change a list to lower case? Keep getting error in for loop

This is the code I have for an exercise on exercism. I want to change the colours typed to lower case just to be sure there won't be any errors. But the way I have now gives me an error on the for loop "the typed string used in the for loop must implement iterable dart". Help?

void main(){
  ResistorColorDuo obj = new ResistorColorDuo();
  obj.result(['Orange','Black']); //I want something that would make these colours lower case so there's no error if someone types it with upper case
}

class ResistorColorDuo {
  static const COLOR_CODES = [
    'black', 'brown', 'red', 'orange', 'yellow', 'green', 'blue', 'violet', 'grey', 'white',];

  void result(List<String> givenColors) {
    String numbers = '';
    for (var color in givenColors.toString().toLowerCase()) {//But this throws an error "the type string used in the for loop must implement iterable dart"
      numbers = numbers + COLOR_CODES.indexOf(color).toString();
    }
    if (givenColors.length != 2)
      print ('ERROR: You should provide exactly 2 colors');

    else
      print (int.parse(numbers));
  }
}

Upvotes: 2

Views: 1619

Answers (2)

HaSnen Tai
HaSnen Tai

Reputation: 1391

Here is the answer. Your mistake was here givenColors.toString().toLowerCase() the givenColors() is a list and list can't be converted to string as you are giving in a for loop. In the below code we take a single value from the list and then convert to the lower case.

This line color.toLowerCase() converts the value to the lower case as color contains a single value from the list on each iteration.

Updated Code

void main(){
  ResistorColorDuo obj = new ResistorColorDuo();
  obj.result(['Orange','Black']); //I want something that would make these colours lower case so there's no error if someone types it with upper case
}

class ResistorColorDuo {
  static const COLOR_CODES = [
    'black', 'brown', 'red', 'orange', 'yellow', 'green', 'blue', 'violet', 'grey', 'white',];

  void result(List<String> givenColors) {
    String numbers = '';
    for (var color in givenColors) {//But this throws an error "the type string used in the for loop must implement iterable dart"
      numbers = numbers + COLOR_CODES.indexOf(color.toLowerCase()).toString();
    }
    if (givenColors.length != 2)
      print ('ERROR: You should provide exactly 2 colors');

    else
      print (int.parse(numbers));
  }
}

Upvotes: 2

Adelina
Adelina

Reputation: 11881

givenColors.toString() converts your list to String; so it can't be iterated;

There are few solutions you can take;

List colorsLowercase = [];
for (var color in givenColors) {
  colorsLowercase.add(color.toLowerCase())
  ...
}

Or like @pskink suggested

givenColors.map((c) => c.toLowerCase())

Upvotes: 1

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