In this blog post, we’ll explore how to resolve a common error in Flutter development when trying to assign a string value to an integer variable. This error often occurs when working with APIs or parsing data from JSON responses.
Understanding the Error
The error message “The argument type ‘String’ can’t be assigned to the parameter type ‘int'” indicates that you’re trying to pass a string value where an integer is expected. This can happen in various situations, such as when parsing data from APIs or JSON responses.
Example 1: Parsing Data from API
Let’s consider an example where we’re fetching data from the SWAPI (Star Wars API). We want to display a list of people with their names and ages. However, when accessing the ‘age’ property of a person object, we encounter the error.
http.get(Uri.parse('https://swapi.co/api/people/'))
.then((response) {
return response.jsonDecode();
}).then((data) {
setState(() {
people = data['results'];
});
}).catchError((error) {
print(error);
});
In this example, the ‘age’ property of a person object is actually an integer value. However, when trying to access it using data[index][‘age’], we get the error.
Example 2: Parsing JSON Response
Another common scenario where this error occurs is when parsing a JSON response from an API. Let’s say we have a JSON object with a ‘name’ property and an ‘age’ property, both of which are strings by default.
{
"name": "John Doe",
"age": "25"
}
When trying to access the ‘age’ property using data[index][‘age’], we get the error. This is because the ‘age’ property is a string, not an integer.
Resolving the Error
To resolve this error, we need to ensure that the value being assigned to an integer variable is actually an integer. In the case of APIs or JSON responses, this often involves parsing the data into its correct type before using it.
Solution 1: Parsing Data from API
One solution to resolve the error is to parse the ‘age’ property as an integer when accessing it. We can use the int.parse() function in Dart to achieve this.
Text(data[index]['name'].toString()) // ... int age = int.parse(data[index]['age']);
Solution 2: Parsing JSON Response
Another solution is to ensure that the ‘age’ property is an integer by default when parsing the JSON response. We can use the jsonDecode() function in Dart to achieve this.
import 'package:convert/json.dart';
Future<Map> fetchPeople() async {
final http.Response response = await http.get(Uri.parse('https://swapi.co/api/people/'));
if (response.statusCode == 200) {
// If the HTTP request is successful, process the returned JSON.
var json = jsonDecode(response.body);
return json;
} else {
// If that was not successful, throw an exception.
throw Exception('Failed to load people');
}
}
// ...
var data = await fetchPeople();
int age = int.parse(data['age']);
Conclusion
In this blog post, we explored how to resolve the error “The argument type ‘String’ can’t be assigned to the parameter type ‘int'” in Flutter development. We covered two common scenarios where this error occurs – parsing data from APIs and JSON responses – and provided solutions to resolve the error.
