I am creating a webpage that contains several area that always look the same. Just wonder does Django support "global" template?
If it does, is there any reference that I can follow. (I try to google "Django global template" but not such similar things comes up).
Thanks!
Django's template inheritance exactly solves this problem. You can create one base template and change just a block that needs to change in the derived sub-pages.
Related
Can anyone tell me if its possible to retrofit inheritance into a Sitecore template?
I have a task to add a new page field into multiple existing templates and I think this should be in a base template.
I've also noticed that the existing templates have fields that should be moved to a base template and then inherited from. Is this possible and if so will there be any side effects with existing code / data?
Yes, it's absolutely ok to add extra base templates to existing Sitecore templates.
E.g. if you already have multiple "page" templates and you need to add extra token for some tracking, you can create new template (let's say "ICustomTracking") and then add it to base templates of your page templates.
To answer your second question: you can "extract" base templates from the existing templates. If you don't want to loose any data, the order of your actions is:
Create new base template
Set this template as a base template for all templates you want it to inherit from.
Move field item from the inheriting template to the base template.
Make sure you move the field item. If you remove the field, and add a new one later, most probably all the data will be lost.
Also it's not recommended to build too complex inheritance structures. It won't be easy to maintain that in the future.
Hoping someone can provide an explain-like-I’m-five elucidation of the difference between the following types of functions within Famo.us, and when it’s appropriate to use them:
sampleFunction() {}
_sampleFunction() {}
SampleView.prototype.sampleFunction() {}
.bind and .call are also thrown around a lot…I understand them vaguely but not as concretely as I’d like. That might be a different question, but please feel free to use them in your explanation!
Apologies for the vagueness...wish there was more regarding this in famo.us university.
None of what you're looking at is syntax specific to Famo.us. It's actually common, if intermediate level, VanillaJS.
The _ is simply a coding convention to denote that a specific function should belong to the parent scope (ie a member/private function, whatever you prefer to call it). Javascript doesn't really have support for encapsulation - the act of blocking other classes and objects from accessing another class's functions and variables. While it is possible, it's quite cumbersome and hacky.
You'll see that Famo.us uses the underscore convention to denote that a function is a member of the class using it. Some of these functions are actually just aliases to the actual Javascript native function, for example ._add actually just call's Javascript's .add method. Of course, ._add could be updated in the future on Famo.us's end to do more in the future if that's required. You really wouldn't want to try and write over the native Javascript add. That's super bad.
The other upshot is that you can document that class and say that you can and should use the _add method for a specific purpose/scenario. You'll see that in the API docs.
Understanding prototype is a core part of what it means to be a Javascript Programmer, after all, it is a prototype driven language. MDN has a much better explanation than anything I can offer here but it's basically at the core of your classes.
If you want to extend off of an existing class (say, create your own View or Surface type) you would extend it's prototype. Check out Famous Starter Kit's App examples and see how many of them create an "AppView" class, which takes the prototype of the core View, copies it for itself, and then adds it's own functions, thus extending View without ruining the original copy.
Is it possible to display all variables available inside a Velocity Template?
Let's say 1 developer pass 2 values to template: $headline and $body. Another developer has to deal with those 2 variables. How would he know names of those variables?
Right now we use 3 solutions:
we simply say what variables are present on templates
we agreed with all developers that all data we pass to template should be included into 1 map ($data)
developer that pass variables to templates has to update template as well and describe all the fields available on it.
I'm looking for way to do this correctly. Right now I'm not really satisfied with all approaches, but 2-nd looks like most preferable.
The short answer is:
$context.keys
The variables and "tools" are accessed by the templates via the velocity "context". If the context tool is available, you can request the list of variables via $context.keys. If not, you need to add the tool ContextTool to the context. How this is done depends on your application.
Although it's technically possible to list all keys in the context, I'm not sure it's also good practice in the situation you describe.
I am using the Poco generator with EF4 and I am wondering if it is possible to edit the T4 template to force all of my entity classes to implement a custom interface. Since the pocos get blown away and recreated each time the custom tool is run, I would have to add this upon each update - I would sure like to avoid that.
I realize I could create partial classes for each poco and implement the interface there, but I was hoping to avoid all that boilerplate code.
Any suggestions would be welcome.
I think I am getting closer to a solution. I am editing the tt template by adding the implemenatation to the signature that is generated.
<#=Accessibility.ForType(entity)#> <#=code.SpaceAfter(code.AbstractOption(entity))#>partial class <#=code.Escape(entity)#> : IEntity<#=code.StringBefore(" , ", code.Escape(entity.BaseType))#>
But I have hit a bit of a snag. Some of my entities have base classes (table inheritance) that I designated in the edmx design. I have need to force all the entities to implement an interface called IEntity. The IEntity contract has no methods so there really is nothing to implement. I will need to rely on all of the entities having a common base. This is due to a completely separate implementation of a custom validation framework. I am getting the proper signatures for most of the entities, however, the entities that already have a base class are throwing a wobbly because you cant implement an interface before you inherit a base class. :IEntity, BaseClass is not allowed. I need to swap those but am not sure how I would pull that off in the template.
On perusing the code in the CodeGenerationTools class that the T4 template uses (found in the include file EF.Utility.CS.ttinclude), I came across this function StringAfter(string value, string append). Therefore, the answer is quite simple, since you state all your entities have to implement IEntity, the following should do the trick:
<#=Accessibility.ForType(entity)#> <#=code.SpaceAfter(code.AbstractOption(entity))#>partial class <#=code.Escape(entity)#> : <#=code.StringAfter(code.Escape(entity.BaseType), "," )#> IEntity
In fact, I know it does because I've tested it :-)
After the T4 template is added to your application, it becomes part of your app and as any other part of the app, you can do whatever you want with it. If for some reason, you don't want to modify the VS added template, make a copy of it and update this to include only the interface implementation. The second way would produce another set of partial files with the custom interface being implemented.
Dont know if this is near what you need but....
I´ve created a Nuget Package that scaffold tiers from T4-templates.
There are default templates for all interfaces (Repository Pattern and UnitOfWork), but you can edit these templates yourself and re-scaffold your system.
To keep it short.. You just install the package (Install-Package CodePlanner) and then define your domainmodel.. And then run "Scaffold CodePlanner.ScaffoldAll"
Its open source (codeplanner.codeplex.com)
Demo: http://average-uffe.blogspot.com/2011/11/codeplanner-011-released-on-nuget-and.html
Edit: The codeplanner package is built for MVC3!
Regards
Uffe
The problem is that if I call a templatetag into a block
and it fills me a variiable with the usual context[varname]=something,
then if I need that variable into another block, I have to call the
templatetag again. This for me means extra db queries, which is really
something I'm trying to avoid.
This templatetag is called in a base template which is extended by
many other templates, so I can't just change all the views to pass
something to the context, it makes no sense (WET principle?)
Even a context processor would be not good because I don't want to
call it for every page rendered in the site, even the ones not based
on that template.
I was thinking about writing a templatetag which would use the
internal context structures to put the variable in a global context,
but I'd feel too guilty doing it.
How would you solve this problem?
You said, "This templatetag is called in a base template which is extended by many other templates."
The question is: is this tag called from within a named block? If it is then you have a couple of potential problems.
{% block %} pushes a new dict on the Context stack and pops it off when it reaches the matching `{% endblock %}'. This means any context value created while in the block has essentially gone out of scope on block exit.
If this block is overridden by some other template that extends the base template, the value may not be available at all unless you do a {{block.super}}, and even then I'm not certain the value will be available to the template doing the extending.
If the tag is not called from within a {% block %} then the context value should be available to all of the code that follows it, either in the base template, any included templates and (I think) any extending templates.
This is one of those cases where building a set of careful tests will probably save you time and tears.
Alternatively, if you are always accessing this value, you could just put it in a context processor so that its availability is guaranteed.
Update for comments: OK, time to bring in the big guns! One of the most irritating, long-standing bugs in Django templates is that callables (ie. functions) that are top-level context values (as opposed to functions that are dict-values/methods of context values) are not called! This ticket is over 2 years old and takes about 10 lines of code to fix. We have several heavy-weight DB calls that we only want to happen if the template cache has expired. So we a) MonkeyPatched the template _resolve_lookup() code to fix the callable problem, and then b) curry functions to have all of the necessary parameters if needed, because you can't pass params to functions in the template "language".
I think you've accurately described the limitations in this situation. The most maintainable solutions will likely involve some restructuring of your template inheritance chain, though its hard to say without knowing the details. Can you introduce a new template in the inheritance hierarchy, probably somewhere near the top of the pyramid but so it only is inherited by templates that need this data, with a single block that encompasses the entire region within which you need this data? That big block can then be subdivided into smaller blocks that inheriting templates will override. If you call your templatetag at the beginning of that block, all blocks within it (including in inheriting templates) will have access to the data.
Update: I can't say much without seeing your templates, but introducing a new template in the middle of an inheritance chain very rarely involves "changing all the templates," in a sane inheritance structure it often can be done with changes to only one or two other templates. And I think what I am suggesting is actually not a hack, it's just better design. If you need a certain piece of data in certain parts of your site and not other parts, there should be a specific single template you can point to and say "this template represents the logical layer at which this piece of data is introduced, and encompasses the parts of the site where that data is needed."
Are you just trying to keep down the number of database queries or are you looking for a clever solution?
If it's the former, I would definitely go with caching. Would fragment caching work in your case? If not, perhaps you could put the caching in the template tag code (assuming it's not one of Django's own template tags your using)?
Just came across this trick from Liviu, Agile Bear (all credit goes to him)
Instead of doing
context['some_var']='some value'
do
context.dicts[0]['some_var']='some value'
May not be a by-the-book-coding-practice but works well enough