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Flutter – How to parse enums from json and ignoring case sesitivity

I have a big enum data like

    enum LargeCategoryEnum{
      numberOne, numberTwo ; 

    factory LargeCategoryEnum.fromJson(String json) =>
      values.byName(json);
 }

and I want to get this enum from a json response but the problem is that the enum in the json response can be all lowercase or all uppercase. for example it can be NumberOne.
So in the LargeCategoryEnum.fromJson it can not map it to any enum name and fails. how can I parse this json?

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3

Answers


  1. 0

    Try the following snippet:

    enum Test{
  
  numberOne,
  numberTwo;
  
  factory Test.fromJson(String name)=>
    
    switch(name.toLowerCase()){
        
      'numberone' => Test.numberOne,
        'numbertwo'=>Test.numberTwo,
        _ => Test.numberOne, // it's a must (exhaustive checking)
    };
  
}

void main() {

  print(Test.fromJson('NumberTWO'));
  
}

    which prints:

    Test.numberTwo

    Switch over the lowercase would be good for small number of values in an enumerated type, while the values number increases you can use the following:

    enum Test {
  numberOne,
  numberTwo,
  numberThree,
  numberFour,
  numberFive,
  numberSix,
  numberSeven;

  factory Test.fromJson(String json) {
    String tempName = '';

    values.forEach((e) {
      if ((e.name.toLowerCase() == json.toLowerCase())) {
        tempName = e.name;
      }
    });

    if(tempName.isEmpty) {
     throw ArgumentError('Incorrect JSON Value : ' , json);
     }
    return values.byName(tempName);
  }
}

void main() {
  print(Test.fromJson('NumberOnE'));
  print(Test.fromJson('NumberTWO'));
  print(Test.fromJson('NumBERTHREE'));
  print(Test.fromJson('NUMBERFOUR'));
  print(Test.fromJson('Numberfive'));
  print(Test.fromJson('NumbeRSIX'));
  print(Test.fromJson('NumberSevEN'));

  print('end');
}

    which prints:

    Test.numberOne
Test.numberTwo
Test.numberThree
Test.numberFour
Test.numberFive
Test.numberSix
Test.numberSeven
end
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  2. 0

    Test.values gives you all the values, so you can compare your string with item.name:

    void main() {
  final value = Test.parse("FIVE");
  
  print(value);
}


enum Test {
  one,
  two,
  three,
  four,
  five;

  factory Test.parse(String value) {
    for (final item in Test.values) {
      if (item.name.toLowerCase() == value.toLowerCase()) {
        return item;
      }
    }

    throw ArgumentError(value);
  }
}
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  3. 0

    My dartbag package has a ParseEnum extension that would let you do:

    enum LargeCategoryEnum{
  numberOne,
  numberTwo;

  factory LargeCategoryEnum.fromJson(String json) {
    var value = values.tryParse(json, caseSensitive: false);
    if (value == null) {
      throw FormatException('Failed to parse: $json');
    }
    return value;
  }
}
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