On 12/01/2011, at 9:54 AM, Sean Van Buggenum wrote:
> Hi all,
>
> I am new to gradle, and am having troubles understanding the order in
> which tasks are run, and what the various keywords (as obvious as they
> sound) actually mean.
There are 2 things to know, which might make this clearer:
* There are 2 different points in time when code related to a task is executed:
The first is configuration time, which is when the build script executes. The
idea is that at this time you configure the task, so that it does the right
thing at the other point in time, namely, execution time. Execution time is the
point in time where the task does its actual work, and happens only if the task
is selected for execution, and after its dependencies have executed.
* Each task has a sequence of actions, which are run in the order specified
when the task executes. An action is simply a closure or an Action
implementation. The doFirst() method configures the task to add an action at
the start of the sequence. The doLast() and << methods configure the task to
add an action at the end of the sequence.
The generic form for a task definition is:
task hello(type: SomeType) {
// this code executes at configuration time, regardless of whether the task
is scheduled for execution
}
The type declaration and the configuration closure are optional. If you leave
out the type declaration, you get a DefaultTask instance.
Sometimes you need to add some behaviour to the task. Sometimes you don't. To
add behaviour, you configure the task to add some actions, using doFirst() or
doLast():
task hello {
// add an action. The action is added at configuration time, but will only
execute at execution time
doLast {
println 'the task is executing'
}
}
Finally, there is a shortcut form for the above:
task hello << {
println 'the task is executing'
}
At the risk of confusing things again:
We're not 100% happy with this syntax. I think that at some point, we will
deprecate and remove this shortcut form as it just doesn't seem to be worth the
confusion it causes.
We are also toying with the idea of deprecating and removing actions, as well.
We'd keep the goodness that doFirst() and doLast() provide, but have it so that
you use tasks instead. This way, there are only tasks.
However, there will be plenty of warning before this happens, so feel free to
use any or all of the above.
--
Adam Murdoch
Gradle Developer
http://www.gradle.org
CTO, Gradle Inc. - Gradle Training, Support, Consulting
http://www.gradle.biz
