CODEWITHSUNDEEP
flutterdart
Hasancan Çakıcıoğlu
Hasancan Çakıcıoğlu

Reputation: 372

how can we use extends in function?

Future dioGet<T extends BaseModel>(String path,T model)async{  
...asdsasa  
}  



abstract class BaseModel<T>{  
  Map<String,dynamic> toJson();  
  T fromJson(Map<String,Object> json);  
}

In the dioGet function above, (T extends BaseModel).What does this do?

does the function return a BaseModel object?

or, the object that will come to the function needs to be extends from BaseModel?

What is T?

Upvotes: 0

Views: 483

Answers (1)

mkobuolys
mkobuolys

Reputation: 5333

First of all, the T inside Future dioGet<T extends BaseModel>(String path, T model) defines a generic type (hence the common short form of that is T) of a model parameter you will pass to the function. This is the official explanation from the Dart language tour:

If you look at the API documentation for the basic array type, List, you’ll see that the type is actually List<E>. The <…> notation marks List as a generic (or parameterized) type—a type that has formal type parameters. By convention, most type variables have single-letter names, such as E, T, S, K, and V.

Now, let's move to the part of what the T extends BaseModel means. By using extend for generic types, you can restrict them and, for instance, only allow passing types that extend/implement a specific type:

When implementing a generic type, you might want to limit the types that can be provided as arguments, so that the argument must be a subtype of a particular type. You can do this using extends.

In the example you provided, only types that extend the BaseModel are allowed to use as a model parameter type in the dioGet function.

Now, to answer your question, it's the second case - the object that comes to the function must extend BaseModel.

Upvotes: 1

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