length of server response in flutter http package - flutter

Question

I am using future builder for building list view. I am getting the response from server. I am getting exactly what i need. There is single error that i am trying to resolve. The error is when i fetch data from server using http.get method : String data=response.body; I am getting the right response that i want and i am parsing it as String catagoeryId=jsonDecode(data)["data"][i]["_id"];
Now the problem i faced when i decode this json i passed this String inside my constructor using for loop. But i have to give length to stop for loop. the length i am using is: data.length. It decode my json response and passes inside my constructor. But after the json length end its stop working and crashed. I checked the length of data.length its something around 344. But i am having only 3 objects. Here is the code i am using for parsing:
Future<List<ProductCatagoery>> getCatagories()async{
http.Response response = await http.get("http://138.68.134.226:3020/api/category/");
List<ProductCatagoery> products=[];
String data=response.body;
for (int i=0;i<=data.length;i++) {
String catagoeryId=jsonDecode(data)["data"][i]["_id"];
String catagoeryThumb=jsonDecode(data)["data"][i]["thumb"];
String catagoeryName=jsonDecode(data)["data"][i]["name"];
bool catagoeryActive=jsonDecode(data)["data"][i]["active"];
print('name is: $catagoeryId : $catagoeryThumb : $catagoeryName : $catagoeryActive');
ProductCatagoery newUser=
ProductCatagoery(catagoeryId,catagoeryThumb,catagoeryName,catagoeryActive);
products.add(newUser);
print('added ${newUser.id}');
print('length is${products.length}');
print('last length data: ${data.length}');
}
return products;
}
Model class:
class ProductCatagoery {
final String id;
final String thumb;
final String name;
final bool active;
ProductCatagoery(this.id,this.thumb,this.name,this.active);
}
Response is:
{"success":true,"data":[{"_id":"5f13cc94c63abc03522eff41","thumb":"category/fresh-meat.jpg","name":"Fresh Meat","active":true},{"_id":"5f13cc73c63abc03522eff40","thumb":"category/fruits-vegetables.jpg","name":"Fruits & Vegetables","active":true},{"_id":"5f13cca5c63abc03522eff42","thumb":"category/grocery.jpg","name":"Grocery","active":true}]}
Note: I just need String data=response.body; data length. I am not using an map etc. I also showed products in list if i return product list after 1, 2 or 3th iteration.

Answer 1

First, decode the response received
final responseFormat = json.decode(response.body);
Then, you can get the list you want to loop with this
final data = responseFormat["data"];
Finally, you can get the length of the list : data.length.
Full code
List<ProductCatagoery> products = [];
final responseFormat = json.decode(response.body);
final data = responseFormat["data"];
for (int i = 0; i < data.length; i++) {
String catagoeryId = data[i]["_id"];
String catagoeryThumb = data[i]["thumb"];
String catagoeryName = data[i]["name"];
bool catagoeryActive = data[i]["active"];
print(
'name is: $catagoeryId : $catagoeryThumb : $catagoeryName : $catagoeryActive');
ProductCatagoery newUser = ProductCatagoery(
catagoeryId, catagoeryThumb, catagoeryName, catagoeryActive);
products.add(newUser);
print('added ${newUser.id}');
print('length is${products.length}');
print('last length data: ${data.length}');
}