Paul Baumann schrieb:
> Holger wrote:
>>> Maybe it would be useful to have a method similar to #sortedBy: in the
> base image
>
> Here are techniques I use for efficient sorting. Given that...
>
> Sorting usually involves multiple attributes. Sorting needs to be fast.
> Determining all the attributes in advance for each of the objects to be
> compared would not be efficient. A general sorting framework should
> allow for the sorting of dissimilar objects without crashing.
>
> Here is an example of how I sort code models of GemKit:
> [snip]
we use something similiar in conjunction with #sortedBy: - a class
called MultiSortKey. It's a subclass of OrderedCollection, and each
element is a sort criteria block.
Example usage (a somewhat constructed example, sorry):
^ self persons sortedBy: [ : person |
MultiSortKey
with: person lastName
with: [ person residence postalCode ]
]
the persons are sorted by name first, then by the postal code. in this
example, fetching the postal code is wrapped in a block, because getting
the residence object might require querying a DB. For sorting this will
only be required for persons with the same last name.
The MultiSortKey basically works like this:
MultiSortKey>>= otherCollection
| size |
self species == otherCollection species ifFalse: [^false].
(size := self size) = otherCollection size ifFalse: [^false].
1 to: size do: [:index |
(self resolvedAt: index) = (otherCollection resolvedAt: index)
ifFalse: [^false]].
^true
MultiSortKey>>resolvedAt: index
" lazy evaluation, value is cached "
| v |
v := self at: index.
v kIsBlock
ifTrue: [
v := v value.
self at: index put: v
].
^ v
_______________________________________________
vwnc mailing list
vwnc@...
http://lists.cs.uiuc.edu/mailman/listinfo/vwnc
