I have an issue with the following Groovy script/
nestedView("JS Pipelines") {
views {
build_pipelines.each {
def build_pipeline = it
buildPipelineView(build_pipeline.build_name + " JS Pipeline") {
selectedJob(build_pipeline.start_job)
}
}
}
}
It requires many calls to the buildPipelineView method, which sits on the views object (code), based on the contents of build_pipelines.
When the call to buildPipelineView is wrapped in each {} call, the method resolves to another buildPipelineView method that is defined in a much higher context. When each block is removed, the method call resolves properly. How can the buildPipelineView resolve properly within each call?
If in doubt store the outer reference, which will be visible to the closure and call this method explicit on that object:
nestedView("JS Pipelines") {
views {
final outer = it
build_pipelines.each { build_pipeline ->
outer.buildPipelineView(build_pipeline.build_name + " JS Pipeline") {
selectedJob(build_pipeline.start_job)
}
}
}
}
In fact, the ContextHelper.groovy of job-dsl-plugin has changed the delegation strategy of the views closure, exactly the brackets of views.
In your case, only the build_pipelines was wrapped in views closure, so you did change the delegation strategy of each closure, but buildPipelineView closure still kept default strategy.
You can use getDelegate to give back the delegation strategy to buildPipelineView closure.
nestedView("JS Pipelines") {
views {
build_pipelines.each {
def build_pipeline = it
def d = getDelegate()
d.buildPipelineView(build_pipeline.build_name + " JS Pipeline") {
selectedJob(build_pipeline.start_job)
}
}
}
}
In nested closures, each one has an owner which is its immediately containing closure. (See Delegation strategy in the Groovy docs.) For the closure you pass to each, its owner is the closure passed to views.
A Groovy closure's default delegation strategy is Closure.OWNER_FIRST, which means when you access a property or calls a method without explicitly mentioning the receiver [like buildPipelineView(...)], Groovy will try to access the property/method on the owner, and if there is none, it'll access the property/method on the delegate.
The straightforward solution is to explicitly provide the receiver, e.g. this.buildPipelineView(...).
Related
What does this syntax mean in Groovy?
class CreateMessagePage extends Page {
static at = { assert title == 'Messages : Create'; true }
static url = 'messages/form'
static content = {
submit { $('input[type=submit]') }
MyVeryStrangeForm { $('form') }
errors(required:false) { $('label.error, .alert-error')?.text() }
}
}
(taken from Spring MVC Test HtmlUnit manual)
The question is about Groovy and I would like know the answer in Groovy terms.
What is content? Is it a static variable? Is its name is random or predefined by base class of Page?
What is = (equal sign) after it? Is it an assignment operator?
What is at the right hand side of =? Is this a closure? Or if this an anonymous class? Or if these are the same?
What is submit inside curly braces?
Is this a variable? Why there is no assignment operator after it then?
Is this a function definition? Can I define functions in arbitrary places in Groovy? If this is a function definition, then what is errors then?
Is submit is a function call, receiving { $('input[type=submit]') } as a parameter? If yes, then where is this function can be defined? For example, where is MyVeryStrangeForm defined (is nowhere)?
If this was function call, then it won't work since it's undefined...
Quick answer to all questions: it's a block of code, like anonymous function, called closure in Groovy.
See http://www.groovy-lang.org/closures.html
In Groovy you can reference/pass/set such closure, as in any Functional Language.
So this:
static at = { assert title == 'Messages : Create'; true }
means that class field at will be set to this closure (notice, not result of closure execution, but closure itself, as block of code). Type of at is omitted there, but it could be static def at or static Object at, or static Closure at
This code could be executed anytime later, in different context, with title defined, etc.
This:
submit { $('input[type=submit]') }
means calling a function submit with closure as argument.
If you want to write own function like this, it should be something like:
def submit(Closure code) {
code.call()
}
Brackets could be omitted, so it could be written as submit({$('input[type=submit]')}). Same for other function as well, it could be println 'hello world!' instead of println('hello world').
There's also a common practice to define closure as last argument, like:
def errors(Map opts, Closure code) {
....
}
at this case you could pass first arguments as usual, wrapped in brackets, and closure outside:
errors(required:false) { ...... }
same to:
errors([required: false], { ..... })
I used the below to see how dart calls methods passed in to other methods to see what context the passed in method would/can be called under.
void main() {
var one = new IDable(1);
var two = new IDable(2);
print('one ${caller(one.getMyId)}'); //one 1
print('two ${caller(two.getMyId)}'); //two 2
print('one ${callerJustForThree(one.getMyId)}'); //NoSuchMethod Exception
}
class IDable{
int id;
IDable(this.id);
int getMyId(){
return id;
}
}
caller(fn){
return fn();
}
callerJustForThree(fn){
var three = new IDable(3);
three.fn();
}
So how does caller manager to call its argument fn without a context i.e. one.fn(), and why does callerJustForThree fail to call a passed in fn on an object which has that function defined for it?
In Dart there is a difference between an instance-method, declared as part of a class, and other functions (like closures and static functions).
Instance methods are the only ones (except for constructors) that can access this. Conceptually they are part of the class description and not the object. That is, when you do a method call o.foo() Dart first extracts the class-type of o. Then it searches for foo in the class description (recursively going through the super classes, if necessary). Finally it applies the found method with this set to o.
In addition to being able to invoke methods on objects (o.foo()) it is also possible to get a bound closure: o.foo (without the parenthesis for the invocation). However, and this is crucial, this form is just syntactic sugar for (<args>) => o.foo(<args>). That is, this just creates a fresh closure that captures o and redirects calls to it to the instance method.
This whole setup has several important consequences:
You can tear off instance methods and get a bound closure. The result of o.foo is automatically bound to o. No need to bind it yourself (but also no way to bind it to a different instance). This is way, in your example, one.getMyId works. You are actually getting the following closure: () => one.getMyId() instead.
It is not possible to add or remove methods to objects. You would need to change the class description and this is something that is (intentionally) not supported.
var f = o.foo; implies that you get a fresh closure all the time. This means that you cannot use this bound closure as a key in a hashtable. For example, register(o.foo) followed by unregister(o.foo) will most likely not work, because each o.foo will be different. You can easily see this by trying print(o.foo == o.foo).
You cannot transfer methods from one object to another. However you try to access instance methods, they will always be bound.
Looking at your examples:
print('one ${caller(one.getMyId)}'); //one 1
print('two ${caller(two.getMyId)}'); //two 2
print('one ${callerJustForThree(one.getMyId)}'); //NoSuchMethod Exception
These lines are equivalent to:
print('one ${caller(() => one.getMyId())}');
print('two ${caller(() => two.getMyId())}');
print('one ${callerJustForThree(() => one.getMyId())}';
Inside callerJustForThree:
callerJustForThree(fn){
var three = new IDable(3);
three.fn();
}
The given argument fn is completely ignored. When doing three.fn() in the last line Dart will find the class description of three (which is IDable) and then search for fn in it. Since it doesn't find one it will call the noSuchMethod fallback. The fn argument is ignored.
If you want to call an instance member depending on some argument you could rewrite the last example as follows:
main() {
...
callerJustForThree((o) => o.getMyId());
}
callerJustForThree(invokeIDableMember){
var three = new IDable(3);
invokeIDableMember(three);
}
I'll try to explain, which is not necessarily a strength of mine. If something I wrote isn't understandable, feel free to give me a shout.
Think of methods as normal objects, like every other variable, too.
When you call caller(one.getMyId), you aren't really passing a reference to the method of the class definition - you pass the method "object" specific for instance one.
In callerJustForThree, you pass the same method "object" of instance one. But you don't call it. Instead of calling the object fn in the scope if your method, you are calling the object fn of the instance three, which doesn't exist, because you didn't define it in the class.
Consider this code, using normal variables:
void main() {
var one = new IDable(1);
var two = new IDable(2);
caller(one.id);
caller(two.id);
callerJustForThree(one.id);
}
class IDable{
int id;
IDable(this.id);
}
caller(param){
print(param);
}
callerJustForThree(param){
var three = new IDable(3);
print(three.id); // This works
print(param); // This works, too
print(three.param); // But why should this work?
}
It's exactly the same concept. Think of your callbacks as normal variables, and everything makes sense. At least I hope so, if I explained it good enough.
Let's consider a simple Groovy DSL
execute {
sendNotification owner
sendNotification payee
}
The implementation of execute is
public static void execute(Closure dslCode) {
Closure clonedCode = dslCode.clone()
def dslDelegate = new MyDslDelegate(owner: 'IncCorp', payee: 'TheBoss')
clonedCode.delegate = dslDelegate
clonedCode.call()
}
and custom Delegate is
public static class MyDslDelegate {
def owner
def payee
void sendNotification(to) {
println "Notification sent to $to"
}
}
The expected result of running execute block is
Notification sent to IncCorp
Notification sent to TheBoss
the actual one is
Notification sent to class package.OwnerClassName
Notification sent to TheBoss
The problem is owner is a reserved property in the Groovy Closure itself and no resolveStrategy options help to replace owner value with custom value from delegate due to Groovy getProperty implementation for Closure
public Object getProperty(final String property) {
if ("delegate".equals(property)) {
return getDelegate();
} else if ("owner".equals(property)) {
return getOwner();
...
} else {
switch(resolveStrategy) {
case DELEGATE_FIRST:
...
}
My question is how some one can outcome this limitation and use owner property name in a custom DSL?
This is a bit of a hack, but this should get you what you want, without altering Groovy source:
public static void execute(Closure dslCode) {
Closure clonedCode = dslCode.clone()
def dslDelegate = new MyDslDelegate(owner: 'IncCorp', payee: 'TheBoss')
clonedCode.#owner = dslDelegate.owner
clonedCode.resolveStrategy = Closure.DELEGATE_ONLY
clonedCode.delegate = dslDelegate
clonedCode.call()
}
Ref: Is it possible to change the owner of a closure?
The simple answer is no, you can't. 'owner' is a reserved keyword in Groovy, and therefore by definition cannot be used as an arbitrary symbol. Even if there is a way to hack around this, you're far better off just using a name that doesn't conflict with the implementation of the language- this is especially true in Groovy, which keeps promising to redesign its MOP completely, meaning that any hack you implement may well stop working in future versions.
Perhaps the question would make more sense if you explained why you are willing to offer a bounty and search for a way of hacking around this problem, rather than just changing the name to something different and avoiding the problem entirely. Reserved symbols are a pretty fundamental limitation of a language, and ever attempting to work around them seems very unwise.
A SoapUI project can run random script upon load.
Load Script is invoked with log and project variables.
In my shared lib I have method - addAsserts() that traverses the whole project and adds schema compliance assertions to SOAP test steps. In my Load Script I call shared method
addAsserts(this)
passing 'this' as a parameter and set closure.delegate to it inside addAsserts method to make 'project' variable accessible within the closure scope
addAsserts method is defined in sharedUtil.groovy:
static def addAsserts(that){
def closure={
project.testSuites.each { testSuiteName, testSuiteObject ->
testSuiteObject.testCases.each { testCaseName, testCaseObject ->
testCaseObject.testSteps.each { testStepName, testStepObject ->
if ("class com.eviware.soapui.impl.wsdl.teststeps.WsdlTestRequestStep" == testStepObject.getClass().toString() ) {
log.info "adding 'Schema Compliance' assertion to ${testSuiteName}/${testCaseName}/${testStepName}"
testStepObject.addAssertion('Schema Compliance')
}
}
}
}
}//closure
closure.delegate=that // <--- i would like NOT to pass 'that' as parameter
// but rather detect in runtime with some kind of
// getCallerInstance() method
return closure.call()
}
QUESTION:
Is it possible to detect caller instance in runtime with some kind of getCallerInstance() method ?
No, I don't believe this is possible. Wasn't in Java either (you can find out the name/method of the calling class using some horrible stacktrace hacking, but not the instance of the class itself)
Edit...
It might be possible with a Category (but I am not experienced with SoapUI, so I don't know if this technique would fit)
Say we have a class Example defined like so:
class Example {
String name
}
We can then write a class very similar to your example code, which in this case will set the delegate of the closure, and the closure will print out the name property of the delegate (as we have set the resolve strategy to DELEGATE_ONLY)
class AssetAddingCategory {
static def addAsserts( that ) {
def closure = {
"Name of object: $name"
}
closure.delegate = that
closure.resolveStrategy = Closure.DELEGATE_ONLY
closure.call()
}
}
Later on in our code, it is then possible to do:
def tim = new Example( name:'tim' )
use( AssetAddingCategory ) {
println tim.addAsserts()
}
And this will print out
Name of object: tim
UPDATE
I have to apologize for confusing the readers. After I got totally lost in the code, I reverted all my changes from Mercurial repo, carefully applied the same logic as before -- and it worked. The answers below helped me understand the (new to me) concept better, and for that I gave them upvotes.
Bottom line: if a call to a missing method happens within a closure, and resolution set to DELEGATE_FIRST, methodMissing() will be called on the delegate. If it doesn't -- check you own code, there is a typo somewhere.
Thanks a lot!
Edit:
OK, now that you've clarified what your are doing (somewhat ;--))
Another approach (one that I use for DSLs) is to parse your closure group to map via a ClosureToMap utility like this:
// converts given closure to map method => value pairs (1-d, if you need nested, ask)
class ClosureToMap {
Map map = [:]
ClosureToMap(Closure c) {
c.delegate = this
c.resolveStrategy = Closure.DELEGATE_FIRST
c.each{"$it"()}
}
def methodMissing(String name, args) {
if(!args.size()) return
map[name] = args[0]
}
def propertyMissing(String name) { name }
}
// Pass your closure to the utility and access the generated map
Map map = new ClosureToMap(your-closure-here)?.map
Now you can iterate through the map, perhaps adding methods to applicable MCL instance. For example, some of my domains have dynamic finders like:
def finders = {
userStatusPaid = { Boolean active = true->
eq {
active "$active"
paid true
}
}
}
I create a map using the ClosureToMap utility, and then iterate through, adding map keys (methods, like "userStatus") and values (in this case, closure "eq") to domain instance MCL, delegating the closure to our ORM, like so:
def injectFinders(Object instance) {
if(instance.hasProperty('finders')) {
Map m = ClosureToMap.new(instance.finders).map
m?.each{ String method, Closure cl->
cl.delegate = instance.orm
cl.resolveStrategy = Closure.DELEGATE_FIRST
instance.orm.metaClass."$method" = cl
}
}
}
In this way in controller scope I can do, say:
def actives = Orders.userStatusPaid()
and "eq" closure will delegate to the ORM and not domain Orders where an MME would occur.
Play around with it, hopefully I've given you some ideas for how to solve the problem. In Groovy, if you can't do it one way, try another ;--)
Good luck!
Original:
Your missingMethod is defined on string metaclass; in order for it to be invoked, you need "someString".foo()
If you simply call foo() by itself within your closure it will fail, regardless of delegation strategy used; i.e. if you don't use the (String) delegate, good luck. Case in point, do "".foo() and it works.
I don't fully understand the issue either, why will you not have access to the closure's delegate? You are setting the closure's delegate and will invoke the closure, which means you will have access to the delegate within the closure itself (and can just delegate.foo())
nope, you will not catch a missing method and redirect it to the delegate with metaclass magic.
the closure delegate is the chance to capture those calls and adapt them to the backing domain.
that means...
you should create your own delegate with the methods required by the dsl.
do not try to force a class to do delegate work if it's not designed for the task, or the code will get really messy in not time.
keep everything dsl related in a set of specially designed delegate classes and everything will suddenly become ridiculously simple and clear.