Using inherited components for web modules
lazarus / 5-Lazarus Extra Components

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Leledumbo · 2011-04-09 16:39

I'm writing a web app using template driven web style, where modules
only handle the content part, while layouting etc. is handled by
parent module.

This approach requires inheritance, as can be seen in the attached
diagram. In this case, IndexModule acts as the one responsible for
layouting, with some default simple actions (usually with only static
content). ProblemModule and ProfileModule should fill the content part
corresponds to the request. For example, if the request is
problem/browse, the content should be filled with a list of problems.
While if it's profile/edit, then an editable form containing user
information should be displayed.

I try to do the inheritance via File->New->Inherited project component
and it's compilable, but when I try to request actions in problem
module, I got this error:
QuoteDuplicate name: A component named "IndexModule" already
existsRequesting IndexModule's actions are fine.

In case anyone needs to see the source, I've attached it as well. It
requires embweb package.

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bobo · 2011-04-15 02:16

I did check out your sample project and tried to understand your
terminology and what you try to achieve.

I think, that to accomplish what you want you don't need any kind of
inheritance.
You do not even need multiple webmodules, just one. Note, you can use
more than one by adding them with File->New->Webmodule,  which is the
correct way to be able to use "index/home", "problem/browse" instead
of what you have tried (index and problem are the webmodule names).
So basically you would have two webmodules, one called "index" another
called "problem" and you could call the actions in these webmodules
the way you have tried.

But this is not needed, you can just use one webmodule with as many
actions as you need. For example, instead of "index/home" the action
would be "ihome" or just "home" and you would not even need to use the
webmodule name in your urls.
Ex: Right now, to call your "index/home" probably looks something like
http://127.0.0.1:8080/cgi-bin/mycgi.exe/index/home (webmodule is
"index" and the action that is called is "home") but it could be
http://127.0.0.1:8080/cgi-bin/mycgi.exe/home instead (by doing this
way, fbweb uses the default webmodule and just calls the action "home"
from there).
Same for problem/browse (calling action "browse" in webmodule
"problem"), it could be just defined in the same webmodule, and called
by http://127.0.0.1:8080/cgi-bin/mycgi.exe/browse
The action names are really irrelevant and for users it does not
matter what the calling URL is.

In fact, you can have just one single webmodule action, handling all
screens by simply using an ID parameter that you can pass.
Ex: http://127.0.0.1:8080/cgi-bin/mycgi.exe/getscreen?id=2  could call
for the content of the current problems/browse action.
Inside the "getscreen" action, you can just check what the passed "ID"
was and generate the response accordingly.

You can even use additional templates for the different screen parts
by using fptemplate.

One more thing, instead of initiating the template settings in the
DataModuleGetAction, you should do it in the DataModuleCreate because
that is only called once, and not for every call (this only matters
for Apache modules and FCGI programs though).

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Leledumbo · 2011-04-15 02:46

QuoteYou do not even need multiple webmodules, just one. ... But this
is not needed, you can just use one webmodule with as many actions as
you need. For example, instead of "index/home" the action would be
"ihome" or just "home" and you would not even need to use the
webmodule name in your urls. ...I need modularity, and using just one
web module isn't a logical way to group actions. index may also have
login and logout action, problem may also have submit and statistic
action. I don't think your suggestion is the intended way to develop
web applications beautifully.
QuoteThe action names are really irrelevant and for users it does not
matter what the calling URL is.It is relevant for the web service part
(on the way).
QuoteOne more thing, instead of initiating the template settings in
the DataModuleGetAction, you should do it in the DataModuleCreate
because that is only called once, and not for every call (this only
matters for Apache modules and FCGI programs though).Unexpectedly,
somehow the actions doesn't get called if I put it there. I know
because there's a postprocessing after the OnReplaceTag, see ~Content
in the template, an this ~Content doesn't get replaced. That's why I
put in OnGetAction (already tried to put it OnCreate before) and the
~Content got replaced.

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bobo · 2011-04-16 01:09

QuoteUnexpectedly, somehow the actions doesn't get called if I put it
there. I know because there's a postprocessing after the OnReplaceTag,
see ~Content in the template, an this ~Content doesn't get replaced.
That's why I put in OnGetAction (already tried to put it OnCreate
before) and the ~Content got replaced.
Then you are doing something wrong. It is working properly with fpweb
for sure.
Do not forget, that if you are using multiple webmodules, then you
need to do the Template init things in all of them, because the
Template property you use is a global property of each webmodule, and
not the Template property of the webactions.
For example, doing a  
Code: [Select]ResponseStr := Template.GetContent;in a webaction event
handler within the "Index" webmodule will access the Template global
property of the "Index" webmodule, and not the "Template" property of
the given webaction (the one you see in the Object Inspector for every
webaction).

Also, you need to create the actions within the proper webmodule for
them to work in the way you've tried to use them in your example.

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Leledumbo · 2011-04-16 18:29

QuoteThen you are doing something wrong. It is working properly with
fpweb for sure.You mean, it 'should'.
QuoteDo not forget, that if you are using multiple webmodules, then
you need to do the Template init things in all of them, because the
Template property you use is a global property of each webmodule, and
not the Template property of the webactions.
...
in a webaction event handler within the "Index" webmodule will access
the Template global property of the "Index" webmodule, and not the
"Template" property of the given webaction (the one you see in the
Object Inspector for every webaction).

Also, you need to create the actions within the proper webmodule for
them to work in the way you've tried to use them in your example.Yeah,
I know. But since problem module inherits index, I suppose calling
Template.GetContent would call GetContent of Template defined in index
module. I'll try to single-step the code to know the request flow.