How can we convert an object to a JSON string in dart?

Overview

We will use the jsonEncode method to convert an object to a JSON string.

The jsonEncode() method is an in-built, top-level function in the dart: convert library, which can convert several types of objects to JSON strings.

There are three steps involved in converting an object to a JSON string:

1. Creating a class
2. Creating a toJson() method. This method returns a JSON object with key/value pairs for all of the class’ fields.
3. Using the jsonEncode() function, and extracting a JSON string from a JSON object.

Implementation

We will create a class named Student with the following attributes:

• name
• id
• age
• department
• level

class Student{
  String name;
  String id;
  int age;
  String department;
  String level;

  Student(this.name, this.id, this.age, this.department, this.level);
}

Next, we will create a toJson() method:

Map toJson() => {
        'name': name,
        'id': id,
        'age': age,
        'department': department,
        'level': level
      };

Note: If the jsonEncode() function is called without creating a toJson() method, an error will be thrown.

Finally, we will convert the Student object to a JSON string, using the dart:convert library’s in-built jsonEncode() function:

String jsonStu = jsonEncode(student);

Now, let’s bring all these pieces of code together to see the output: