Hi all,
Over the years, I’ve worked on an class for doing ad hoc queries. This class has gotten better and better. At first, the API of this class and some implementation details were not ready for public consumption in my opinion.
However, recently I took the time to polish the code as much as possible and if I can get my employer's approval I would like to contribute this code to project Wonder which has given us so much in return during the years.
Here is a preview of its functionality. Please let me know if you guys think this would be a useful contribution. ERXQuery.java
This class has a fluent API that mimics a select statement: NSArray<NSDictionary<String,Object>> records =
ERXQuery.create()
.select (keys)
.from (entity)
.where (qualifier)
.groupBy (groupings)
.having (havingQualifier)
.orderBy (sortings)
.fetch();
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Overview ERXQuery allows you to use EOF constructs (EOQualifiers, EOAttributes, EOSortOrdering, EOAttribute names, relationships, etc.) to create queries of the form:
SELECT ...
FROM ...
WHERE ...
GROUP BY ...
HAVING ...
ORDER BY ...
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Using Ad Hoc Attributes You may use the ERXAdHocAttributes class to easily create ad hoc attributes to use with your query. For example, the code below creates two ad hoc EOAttributes. An ad hoc attribute is an EOAttribute that is not physically attached to an entity and that has a definition. They are useful for aggregating other attributes. The definition of the attribute can reference relationships and attributes as shown below. ERXAdHocAttributes attributes = ERXAdHocAttributes.create(orderEntity)
.add("itemCount", "COUNT(DISTINCT lineItems.lineItemID)", "intNumber")
.add("orderCount", "COUNT(DISTINCT orderID)", "intNumber");
NSDictionary<String,Object> row =
ERXQuery.create()
.select (attributes)
.from (orderEntity)
.where (qualifier)
.fetch()
.lastObject();
int orderCount = ((Number) row.objectForKey("orderCount")).intValue();
int itemCount = ((Number) row.objectForKey("itemCount")).intValue();
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Fetching into a Custom Record ClassYou can also fetch using a custom class of your choice, i.e. Foo, as shown below: NSArray<Foo> objs = query.fetch(editingContext, (ec, row) -> new Foo(ec, row));
ERXQuery.RecordConstructor<Foo> recordConstructor =
new ERXQuery.RecordConstructor<Foo> {
@Override
public Foo constructRecord(EOEditingContext ec, NSMutableDictionary row) {
return new Foo(ec, row);
}
};
NSArray objs = query.fetch(editingContext, recordConstructor);
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Author: Ricardo J. Parada |