I'm currently writing an application that plays podcasts. I'm representing all the feeds and the episodes within them as QStandardItem objects within a QStandardItemModel. Right now, I don't have a way to save this model--when the application closes, the feed model goes up in smoke. I looked at using QSettings, but that only works for datatypes that fall under QVariant.
Looking at this post gave me some hope, but I think I'm doing something wrong. I've got the following code in the constructor for my application.
//Expand QVatiant to use QStandardItemModel
qRegisterMetaType<QStandardItemModel>("QStandardItemModel");
That, however, gives me this error at compile time.
/ [...] QtSDK/Desktop/Qt/4.8.1/gcc/lib/QtGui.framework/Versions/4/Headers/qstandarditemmodel.h:424: error: 'QStandardItemModel::QStandardItemModel(const QStandardItemModel&)' is private
Ah. That reminds me of this caveat from the Qt documentation for QMetaType, here.
Any class or struct that has a public default constructor, a public copy constructor and a public destructor can be registered.
So, where do I go from here? Qt is behaving exactly as it should, so this approach won't work. I'm thinking of saving off the model as an xml file, but that seems like a ton of effort. This seems like a pretty common problem--I just don't know where to look for the answer.
Here's the best solution I could come up with: Create a method that saves the model into an XML document, and call it whenever I change the model (e.g. add or remove a podcast). I don't have the actual source code on hand, but since there's no real easy way to save the data structure wholesale, this is the best solution.
Related
This question could apply to all languages and frameworks but I'm looking for something a bit more 'cocoa specific'. I come from a Java background and I've noticed that learning objective-c is a lot more than just syntax, it's almost a completely different way of thinking.
What I've been having the most trouble with, must be the way one has to organise your classes. Sure all basic OOP(Object Oriented Programming) rules apply, and using MVC patterns where you can is recommended. But with me being used to Java I just need to set a few things straight and make sure I've got the right idea:
So for the sake of simplicity let just focus on one part of an app - Logging a user in. You'd have your .xib file for the UI (called Login.xib), you'd have your class that handles your data (connecting to a web service, called LoginModel.m) and you'd have your controller that acts as the middle man between your front-end and data (Called LoginController.m).
Is this is a pretty good example of applying MVC to a Cocoa app? And if it is, does that mean that you'd have 6 files created for this (since you have header files and implementation files). 6 files just to handle something simple as logging a user in. You can imagine how many you'd end up with for an entire app, even the most simplest of ones...
So my question is - Am I doing something wrong? Do I have the wrong idea? Or is the idea of too many files and too long method names just something I need to get used to since my brain is still working in 'Java Mode'?
Your ideas on how to handle that outlined above are fully correct. There is nothing bad about having a lot of files in the project. It does help a lot when you want to reuse code or if for example login details change and you don't want to edit multiple code locations.
Nevertheless, you may combine in such simple cases model class and controller class, especially if your model data can for example be stored in an NSDictionary and such. Only if you have complex model objects, that will run a lot of their own code, it will be better to separate them out.
Variable and method names can't be too long ;) always use a good name that especially describes the functionality or task. You usually don't have to type them often, but Xcode autocomplete will deal with that easily.
I am brand new to Magento and the documentation, primarily the phpDocs, are difficult to navigate. For example,
$attributeSet = Mage::getModel('eav/entity_attribute_set')->load($id);
In the php doc for Class Mage_Eav_Model_Entity_Attribute_Set there is no mention of the method getAttributeSetName() either in inherited methods or otherwise and yet this works.
$attributeSet = Mage::getModel('eav/entity_attribute_set')->load($id);
echo $attributeSet->getAttributeSetName();
So I suppose I have several questions.
Can someone explain to me why the documentation is this way?
Where I can find the mysterious getAttributeSetName() method in the phpDocs?
My theory is that there is some inheritance or a design pattern implementation going on that I'm not understanding, maybe someone can shed some light on this for me.
If you really want to fry your brain, take a look at the source code for Mage_Eav_Model_Entity_Attribute_Set and follow the inheritance chain all the way back. You won't find a getAttributeSetName method defined anywhere.
All Magento objects that inherit from Varien_Object can have arbitrary data members set on them. Try this.
$attributeSet = Mage::getModel('eav/entity_attribute_set')->load($id);
$attributeSet->setFooBazBar('Value');
var_dump($attributeSet->getFooBazBar());
var_dump($attributeSet->getData('foo_baz_bar'));
var_dump($attributeSet->setData('foo_baz_bar','New Value'));
var_dump($attributeSet->getFooBazBar());
You can also get all the data members by using
var_dump($attributeSet->getData());
but be careful dumping these, because if there's a data object that has a circular reference and you're not using something like xDebug, then PHP will have a fit trying to display the object.
Magento stores data properties in a special _data array property. You can get/set values in this array with getData and setData. Magento also has implemented magic getting and setter methods, so when you say something like
$object->getFooBazBar();
The method getFooBazBar is transformed into the data property foo_baz_bar. and then getData is called using this property. It's a little tricky to get your head around, but once you get it you'll start to see how much time you can save using this pattern.
One side effect of this is, of course, it's impossible to infer what data properties any object might have by looking at it's class file, so there's no phpDocs for these methods.
I have a little problem, I need to load some json data to my grid, but I have specifical json format like this:
{"response":[
76297,
{"aid":66132303,"owner_id":30729520,"artist":"Шакира - Танго","title":"So objection!! I don't wanna be the exception to get a bit of your attention... I love you for free and I'm not your mother, but you don't even bother... Objections!! I'm tired of this triangle... GOT DIZZY DANCING TANGO","duration":224,"url":"http:\/\/cs1663.vkontakte.ru\/u17640367\/audio\/ebde4092fde5.mp3","lyrics_id":"2203614"},
{"aid":129159521,"owner_id":23962687,"artist":"Yann Tiersen","title":"Mother's Journey (Ennja Remix)","duration":281,"url":"http:\/\/cs6000.vkontakte.ru\/u97497795\/audio\/fb309491bc82.mp3","lyrics_id":"21301612","album":"21017129"},
{"aid":81267321,"owner_id":673065,"artist":"Hurts","title":"Mother Nature","duration":170,"url":"http:\/\/cs4633.vkontakte.ru\/u673065\/audio\/d329378eb2d2.mp3","lyrics_id":"5693202"}]
}
So the first element of array is number of total records, and others are the records to load.
If I try to load such records to my grid I have empty row at the bottom, what is a solution? Should I use some "custom" reader, how to implement it?
Yes. Most likely you would need to extend standard Json reader (Ext.data.reader.Json) to parse length first and start parsing records from the second item.
Update: It's quite easy to do actually.
First you need to figure our place where standard reader doesn't behave the way you want it to behave. Add traces to standard reader class, to see what's going on. Most likely it will be somewhere around readResponse() method.
Create your own reader class extending standard one. Simple inheritance.
Override method you need with new logic.
ExtJs code is very well written and commented. I found it's quite interesting to read and understand it.
As a side note I would add that this task (extending existing ExtJs code with your functionality) is a huge help to better understand how ExtJs works inside and you will feel much more confortable working with ExtJs after that.
I have some weeks since im using CI, but now I've found some problems about the structure of my project, I would like someone to give me some clues because I am kinda stuck, the problem is this:
I have my project MVC, so, I am dividing it into files (each per functionality) for example, there is a file with all the functions corresponding at login, and other with all related at post (it's an example), but now I am on a moment where I need to use login or posting into another part of the project, reading I found out i cannot call a controller from another, I can use the helper but still I will need to use a model, so I have to take that code and paste it into the controller where I'm calling the model and so on (and it's not good), I found out I can use modules, still I don't want to go over them until someone could give me an experience of this, i wouldnt like to change the project, is any way I could run all those controllers (i know i can use run:: I'm not sure if i can send parameters in it), any ideas please?
Thanks in advance.
Fair warning, this type of question will get shot down by many SO moderators, but I'll give you some tips regardless:
Controller actions are single-use. If you find yourself with duplicate code in multiple controllers (or, needing to call a controller function from another controller), that's a sure sign you should move that code to a model or library.
Models are object-specific, not action-specific. I wouldn't have a model dedicated to logins, unless you have multiple types of logins (most apps/sites just have member logins, but you might have administrators, etc. that are stored in a different table from the rest). Instead, have a User_model class, and make function login($email, $password) a method of that class.
Controller-to-model interaction should be very concise. If you find yourself with 30 lines of code passing data back and forth between the same controller and model, you might be trying to do too much with that one controller action.
Keep your models fat, controllers skinny, and views dumb.
Ok, I am creating a document-based application in Cocoa and the document's file type is actually a package. Within that package is an XML settings file, a SQLite database and a zip file which is downloaded at runtime. Now the only thing that changes, really, is the XML settings file as the other ones can be recreated at run-time.
Each one of these packages will have one and only one window, hence my desire to use document-based. These files can also be copied, renamed, moved, etc. just like any other file that is part of such an architecture.
But I am completely lost as how to implement this in the Documentation Framework! It seems everywhere I look in the docs it's always talking about in-memory representations of the files which you then write out using the path presented to you in one of the NSDocument overrides (since Cocoa may move it, etc.) But again, I'm using a SQLite database that sits on disk, not in memory.
I have looked all over for overridable methods that would still give me things like dirty-state checking of the doc, open and save file dialog support and the like, but I can't seem to find anything that just says 'Here's a file URL... Open it as you see fit' althought I did get close at the application's delegate level, at least for the opening.
So let's assume that's working as expected. How do I implement the save/save-as where I want to control everything that is written to disk or not? I don't want to (not can I) mess around with data structures or the like. I just want to be given a psth that the user selects in the 'Save As' dialog (for new) and be able to write what I need to there. Simple. But again, the 50+ page document from developer.apple.com about Document-based architecture tells me where to overload a lot of things, but every one seems to stem from some in-memory representation of the document, which again, is not what my package is. Technically, only the internal XML file is what would be tied to the document. Everything else is just support for it.
So? Anyone? Takers?
Mark
I can't seem to find anything that just says 'Here's a file URL... Open it as you see fit'
Implement the readFromURL:ofType:error: method in your document class. Alternatively, since your document type is a package type, implement the readFromFileWrapper:ofType:error: method.
You don't have to read the data into memory; you can do whatever you want in whichever method you implement, including opening the database.
How do I implement the save/save-as where I want to control everything that is written to disk or not?
Implement the writeToURL:ofType:error: method or the fileWrapperOfType:error: method.
If you had or could easily create data in memory, you would implement the readFromData:ofType:error: and dataOfType:error: methods. The URL-based and file-wrapper-based methods are for cases where data in memory is not an option. And the primary use of file wrappers is for package types like yours.
Actually, I found it. It's not the 'writeTo' methods, but rather the 'saveTo' methods you want to override. When I did that, the saving code worked as I expected, including automatic save panel support. For clarity, this is the one I chose...
saveToURL:ofType:forSaveOperation:error:
and it works like a champ! Not too confusing now, was it! Sheesh!!!
That was of course the very first thing that I tried, but if you read the developer documentation--specifically the Cocoa Document-Based Architecture--here's what it says about those very methods...
During writing, your document may be asked to write its contents to a different location or using a different file type. Again, your overridden method should be able to determine everything it needs to do the writing from the passed-in parameters.
If your override cannot determine all of the information it needs from the passed-in parameters, consider overriding another method. For example, if you see the need to invoke fileURL from within an override of readFromData:ofType:error:, perhaps you should instead override readFromURL:ofType:error:. For another example, if you see the need to invoke fileURL from within an override of writeToURL:ofType:error:, perhaps you should instead override writeToURL:ofType:forSaveOperation:originalContentsURL:error:.
In other words, it seems to say that you can't assume the URL that is passed to you is the actual place on disk where the 'something' is eventually written to, which wreaks havoc when dealing with database files that are opened by URL. Maybe I'm missing something.
But ok... forget I read that and simply even try to just override those methods. I do and return TRUE for each, (I log the URL so I can see what is being passed in), I get this error on 'Save As' after you have chosen a filename...
2009-10-28 14:31:51.548 XPanel[1001:a0f] dataOfType:error: is a subclass responsibility but has not been overridden.
...but when you look at the documentation for that it says the default implementation throws an exception because you must override one of the other implementations above... which I obviously just did! Plus, again, this can't be represented as simple data!
So grasping at straws here, I overrode that one too and just returned nil, since again, you can't represent what I'm doing with a NSData object. Then I get a 'Can't be saved' message.
WTF?! Why is it calling that thing anyway??!!
...and that's when I gave up and posted this here.
Now if YOU can give me a simple example that perhaps doesn't even actually read or write a file but instead just logs the URL, that would be perfect. Not to useful but still, it should work... I just can't seem to implement get it to.