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https://issues.apache.org/jira/browse/METAMODEL-145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14567050#comment-14567050
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xialvjun commented on METAMODEL-145:
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Assume a Class Person has String name, Integer age, String sex 3 properties.
Can TypedColumn<Person> mean [TypedColumn<String>, TypedColumn<Integer>,
TypedColumn<String>]. Then if I set a filter where(TypedColumn<Person> ==
Person p), it means where(TypedColumn<String> == String
pname).and(TypedColumn<Integer> == Integer page).and(TypedColumn<String> ==
String psex)......balabalabala.....
Also, we can group by the TypedColumn<Person>
> A Column subinterface with type arguments
> -----------------------------------------
>
> Key: METAMODEL-145
> URL: https://issues.apache.org/jira/browse/METAMODEL-145
> Project: Apache MetaModel
> Issue Type: New Feature
> Reporter: Kasper Sørensen
>
> I propose to introduce a new interface to extend the Column interface. This
> interface should have a type parameter, representing the value type of the
> column. My suggested name would be TypedColumn<E>.
> To take advantage of this type information I propose a few changes:
> DataSet: Add a getValue(TypedColumn) method. When you have a typed column you
> can then get values from DataSets that do not need casting:
> {code}
> TypedColumn<Boolean> c1 = ...
> TypedColumn<String> c2 = ...
> DataSet ds = ...
> Boolean value1 = ds.getValue(c1);
> Boolean value2 = ds.getValue(c2);
> {code}
> Table: Change the return type of getNumberColumns() to return TypedColumn<?
> extends Number>[] instead of just Column[]. Apply same principle to other
> such methods (getBooleanColumns, getLiteralColumns etc.).
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