Delegate Usage : Business Applications

Question

Background

Given that \'most\' developers are Business application developers, the features of our favorite programming languages are used in the context of what we

Answer 1

One common pattern I've seen over the years (in various languages) is to "freeze" the result of a decision to move logic out of a loop into a setup. In pseudo-code (because the technique varies with language):

some_condition = setup_logic
...
while (not terminated) {
    data = obtain_data
    if (some_condition)
        process_one (data)
    else
        process_two (data)
}

The point is that if some_condition doesn't change based on anything in the loop, then there's really no benefit from repeatedly testing it. Delegates/closures/etc. allow the above to be replaced by this:

some_condition = setup_logic
if (some_condition)
    selected_process = process_one
else
    selected_process = process_two
...
while (not terminated) {
    data = obtain_data
    selected_process (data)
}

(Of course, a Real Functional Programmer would have written the setup as:

selected_process = if (some_condition) process_one else process_two

;-)

This generalizes nicely to multiple alternatives (instead of just two). The key idea is to decide in advance what action to take at a future point (or points), and then remember the chosen action rather than the value on which the decision was based.