silverstripe/sapphire — pull request #1020 by hafriedlander (2012-12-12 04:37:34+00:00)
Title: API Make DataList and ArrayList immutable

In 3.0 there was some confusion about whether DataLists and ArrayLists
were mutable or not. If DataLists were immutable, they'd return the result, and your code
would look like

$list = $list->filter(....);

If DataLists were mutable, they'd operate on themselves, returning nothing, and your code
would look like

$list->filter(....);

This makes all DataLists and ArrayList immutable for all _searching_ operations.
Operations on DataList that modify the underlying SQL data store remain mutating.

- These functions no longer mutate the existing object, and if you do not capture the value
returned by them will have no effect:

ArrayList#reverse
ArrayList#sort
ArrayList#filter
ArrayList#exclude

DataList#dataQuery (use DataList#alterDataQuery to modify dataQuery in a safe manner)
DataList#where
DataList#limit
DataList#sort
DataList#addFilter
DataList#applyFilterContext
DataList#innerJoin
DataList#leftJoin
DataList#find
DataList#byIDs
DataList#reverse

- DataList#setDataQueryParam has been added as syntactic sugar around the most common
cause of accessing the dataQuery directly - setting query parameters

- RelationList#setForeignID has been removed. Always use RelationList#forForeignID
when querying, and overload RelationList#foreignIDList when subclassing.

- Relatedly,the protected variable RelationList->foreignID has been removed, as the ID is
now stored on a query parameter. Use RelationList#getForeignID to read it.