CODEWITHSUNDEEP
genericsgwt
XX Terror
XX Terror

Reputation: 55

Generics polymorphism in GWT

class ModelImpl extends Model {

...

CellTable<? extends Model> tableImpl;

...

tableImpl=new CellTable<ModelImpl>();

...

and finally ...

    TextColumn<ModelImpl> column = new TextColumn<ModelImpl>() {
      @Override
      public String getValue(ModelImpl object) {
        return object.getColumnValue();
      }
    };
    tableImpl.addColumn(column, "nameColumn");

compiler says:

cannot find symbol method addColumn(com.google.gwt.user.cellview.client.TextColumn < ModelImpl > ,java.lang.String)

but ModelImpl extends Model!! Whats happening?

Upvotes: 1

Views: 585

Answers (1)

ben_w
ben_w

Reputation: 736

The problem is that you have defined tableImpl with the type CellTable<? extends Model>.

? extends Model means "some specific subclass of Model, but I am not sure what it is".

addColumn has the signature:

public void addColumn(Column<T,?> col)

The problem is, the you have lost what T is, because tableImpl is of type CellTable<? extends Model>. addColumn only takes a column of the exact same kind of T that the CellTable is parameterized by (in your case ModelImpl). But you have stored your CellTable in a variable that does not know what that exact type is.

So change tableImpl's definition to look like:

CellTable<ModelImpl> tableImpl;

Upvotes: 4

Related Questions