toJson

Serialize a model to JSON with toJson.

The toJson method

To convert a model to JSON you write a toJson method. It returns a Map<String, dynamic>; the keys are JSON field names and the values are the model's fields. You can turn the returned Map into a JSON string with jsonEncode.

class Kullanici {
  final String ad;
  final int yas;
  Kullanici(this.ad, this.yas);

  Map<String, dynamic> toJson() {
    return {'ad': ad, 'yas': yas};
  }
}

final k = Kullanici('Ada', 19);
print(jsonEncode(k.toJson()));
// {"ad":"Ada","yas":19}

When is toJson useful?

toJson usually contains a simple return statement; you write each field as a key-value pair inside the Map. This method is especially useful before sending data to a server or storing it with shared_preferences.

Map<String, dynamic> toJson() {
  return {
    'ad': ad,
    'yas': yas,
  };
}

Exercise Write the toJson method

Add a toJson method to the Kullanici class. In main, convert the toJson output of k to a JSON string with jsonEncode and print it with print.

Show example solution

import 'dart:convert';

class Kullanici {
  final String ad;
  final int yas;

  Kullanici(this.ad, this.yas);

  Map<String, dynamic> toJson() {
    return {'ad': ad, 'yas': yas};
  }
}

void main() {
  final k = Kullanici('Cem', 35);
  print(jsonEncode(k.toJson()));
}

Test yourself

What is the return type of the toJson method?
- Map<String, dynamic>
- Future
- void
- String
Show answer

Map<String, dynamic> — toJson returns a Map; this Map is later converted to a JSON string with jsonEncode. void returns nothing, String is not direct, and it is not async.

Write the toJson body

class Kullanici {
  final String ad;
  final int yas;
  Kullanici(this.ad, this.yas);

  Map<String, dynamic> toJson() {
    ____;
  }
}

Show answer

class Kullanici {
  final String ad;
  final int yas;
  Kullanici(this.ad, this.yas);

  Map<String, dynamic> toJson() {
    return {'ad': ad, 'yas': yas};
  }
}

toJson parts

Map<String, dynamic>

Return type
'ad': ad

Key-value pair
return {...}

Map return
jsonEncode

Conversion to JSON string

Next lesson: List model

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