I'm trying to figure out how to create a new object template at runtime (created by the user) and then use that template to create new objects to populate a list. For example, say you want a list of contacts. The user would create a template that has an NSMutable array of generic objects which contain name, phone, email, etc. Then when they are done creating the template, they can then add a new contact based on that template anytime they want without rebuilding the template. All the template object would consist of is the generic object nested inside of itself with it's value set as different data types, then all those generic objects stored inside of another generic object that contains just an array. I hope I'm not making this sound too confusing... Basically just the ability to create custom object templates at runtime, then be able to use those. Anyone know of a good approach to this? I'd like to make the data storage in my app universal so it can apply to anybody's data. Thanks.
I'm not exactly sure what your final goal is, but you could take an 'Interface Builder' approach. You have your view to build the template, and then you convert every element to xml form. All you would have to do to load it is read the xml, create the appropriate UI elements, and add them at the right location in a container view. One problem with this approach is if you need to send data to an element, it would be almost impossible to get the right element if there are multiple of that type in your template. You could use an array, dictionary, or even the xml to store a key (the name of the element), and a value (the element, this would not be required using the xml approach). Sorry if this is confusing.
There are several viable options for reading and writing objects to the disk on iOS. The most famous and widely used being Core Data and Plists.
If you are a beginner, I would recommend saving an array of attributes (possibly as strings?) for a custom object 'template'. See here for a tutorial, and search SO for anything else that might come up.
Related
I need to store an activity feed in an iOS application. Activity feed items will have a payload field which can be one of many (and I really mean many) types of entities in the system.
What is a good way to implement this payload relationship field on the Activity entity in my CoreData model?
Is it possible to use the id data type, or maybe use an NSManagedObject type?
One way to workaround this maybe to just store CoreData's entityId as a string in a special field, but I'd rather avoid that if there is a better way.
Example:
For simplicity let's say we have a not-so-standard blogging model: User, Blog, BlogPost, Comment and the following activities may happen:
User may create a new blog.
User may publish a new blog post.
A blog can be commented on.
A comment maybe liked.
etc.
Each of these generate a new Activity item on the website which in turns have a related payload relation to the item that was modified or being acted on.
Now I need to download, translate and store these activity feed items from the website in my iPhone application... so how do I mimic this payload field since it maybe pointing to any possible entity?
In my real code, though, there are about 10+ types of entities that could be put into this payload field so I'm looking for a good approach here.
If you don't need to search / query the fields of your objects of variable type, then I suggest to use NSCoder to convert them into a binary representation and store them in a BLOB field of your managed object. You might want to store some type information as well in an other field of the same managed object. On the other side if you need to search between these variable objects then you have to create a new managed object type (entity) for each object. See my answer also here: NSCoding VS Core data
Only thing that you can use is NSManagedObject. So you have to create your model and your relation and create new file for Activity and payload that will be subclasses of NSManagedObject.
Take a look at Core Data Programing Guide .
You will find your answers in there.
I'm trying to get the hang of MVC architecture. Say I have a plist in which there are a list of persons and each person has a few attributes like name, address and photograph. Suppose
I want to display these details in a table view. The cell title would be the name, description would be the address and the image towards the left would be the photograph of the person.
One approach I could take is to load the plist in an array-of-dictionaries in my viewDidLoad: and then display them.
However, I want to adopt an Object Oriented method by creating 'Person' class. How do I go about doing the same in this case? I believe I could start by creating a 'Person' class with three attributes:Name, Address, Photograph. What next? I would need many instances of this 'Person' class right? How would I 'load' each instance with a corresponding Person entry from the plist? Should I create another class that does this 'loading'? Do people use Singleton class to achieve his?
Could someone share some sample sample code to illustrate this? Or maybe guide me to blogs/resources that talk about this?
Hmmm, I think you are over thinking this a bit. I would just create a class that would handle my person, in this case your 'Person' class.
I would simply store each person using Core Data. Then, when it's time to display them, I would just make a fetch request and store all person managed objects into an NSMutableArray (which simply handles arrays of objects). Then you can simply use the index value to display the numerous persons in your array in a tableView.
In summary I would:
1. For every person, create instance of Person.
2. Verify if person exists in my Core Data Person Entity.
3. If not, then insert into Core Data (the object will become an
NSManagedObject).
4. For displaying, simply do a fetch request to pull all persons in your
entity. Here I prefer to store the
results into an NSMutableArray, but
that is completely up to you. Make
sure you release your fetch request
after the results are store in the
array.
5. Reference them to your table view using the index value for each
person NSManagedObject in the array.
For something that doesn't involve storing simply:
1. Create instance of Person for every entry.
2. Add Person object to array.
3. Reference each Person to table view using index value.
In the end the approach that you take will be dictated by what you want to do with the information.
As for reading the plist, I would opt for reading an XML for which all you need is an XML Parser class (there are several options for parsers). Since I don't do anything but parse the XML, I use NSXMLParser, but that choice is also up to you. Just create an NSXMLParser class (make sure that the different actions for when the parser finds a given element are in play inside that parser). So yes, you would need to make additions to the NSXMLParser for handling each element. It's really easier than it sounds.
Also, by storing in Core Data, you can always fetch the info without you using a Singleton.
I believe you are not looking for a design solution to the above mentioned question. If that is the case #A Salcedo 's version looks fine.
if you are looking for general guide lines for MVC and modeling , Martin Fowler's site offers some of the best (agile) design/modeling guidelines.
http://www.martinfowler.com/eaaDev/uiArchs.html (on MVC) and
http://martinfowler.com/design.html (many interesting design related posts).
Happy reading.
I want to pass data to views, and I've two options in my mind (if you know a better approach, please mention).
I am using Zend_Based ORM system, and coded in a way that if I add a new field in database, its automatically available within the model.
1st: I convert the model's data into array and pass the array to the view. This way I will have all the data available within the view, but model's function/operations will not be available. And incase I need specific functionality, i will be coding view helpers while there are chances that the same functionality is already coded within model. e.g. a getting a date in specific format.
2nd: Or I pass the complete model object to the view, this way I will have all the model's functions available, but view will be able to access model's save function which is a bad thing. I can add some more functionality within model to make it read-only, but it will be extra work.
any suggestions which approach is better.
According to the MVC principle it's perfectly fine to let the View allow access to the Model. So, pass the complete Model to the View.
By the way, passing arrays around will copy your data (by value), while passing objects around will not (by reference). (Assuming PHP5). Large arrays might affect your performance.
I have started developing my own web framework which has been coming along quite nicely. It simplifies and cators for all my specific needs. I have tried many frameworks like struts, struts 2, tapestry, spring and the list goes on. There are 2 big problems I find in all of these frameworks.
The ability to work with specific business logic/rules.
I am a bit of a perfectionist and the entire layout of these frameworks force you to scatter you validation, DAO logic and your form actions. I like to keep things grouped together and not do validation in my Hibernate Objects, Action classes and a separate XML files which causes a load unnecessary processing.
Ok back to my question. Does any one know of possible solutions to populating Objects from a HTTPRequest? I started looking into introspection and reflection, but I would like to see if there might be a better solution for something like this. Example: Object Student has 3 fields eg String Name, Integer age and Calendar DOB. What are the options in populating this object or any other Object from a HTTPrequest?
You could use a similar system to the way objects are sent in json by adding a __type__field that gets sent with each object. That way you know which object to create and introspect.
I would like to experimentally apply an aspect of encapsulation that I read about once, where an entity object includes domains for its attributes, e.g. for its CostCentre property, it contains the list of valid cost centres. This way, when I open an edit form for an Extension, I only need pass the form one Extension object, where I normally access a CostCentre object when initialising the form.
This also applies where I have a list of Extensions bound to a grid (telerik RadGrid), and I handle an edit command on the grid. I want to create an edit form and pass it an Extension object, where now I pass the edit form an ExtensionID and create my object in the form.
What I'm actually asking here is for pointers to guidance on doing this this way, or the 'proper' way of achieving something similar to what I have described here.
It would depend on your data source. If you are retrieving the list of Cost Centers from a database, that would be one approach. If it's a short list of predetermined values (like Yes/No/Maybe So) then property attributes might do the trick. If it needs to be more configurable per-environment, then IoC or the Provider pattern would be the best choice.
I think your problem is similar to a custom ad-hoc search page we did on a previous project. We decorated our entity classes and properties with attributes that contained some predetermined 'pointers' to the lookup value methods, and their relationships. Then we created a single custom UI control (like your edit page described in your post) which used these attributes to generate the drop down and auto-completion text box lists by dynamically generating a LINQ expression, then executing it at run-time based on whatever the user was doing.
This was accomplished with basically three moving parts: A) the attributes on the data access objects B) the 'attribute facade' methods at the middle-tier compiling and generation dynamic LINQ expressions and C) the custom UI control that called our middle-tier service methods.
Sometimes plans like these backfire, but in our case it worked great. Decorating our objects with attributes, then creating a single path of logic gave us just enough power to do what we needed to do while minimizing the amount of code required, and completely eliminated any boilerplate. However, this approach was not very configurable. By compiling these attributes into the code, we tightly coupled our application to the datasource. On this particular project it wasn't a big deal because it was a clients internal system and it fit the project timeline. However, on a "real product" implementing the logic with the Provider pattern or using something like the Castle Projects IoC would have allowed us the same power with a great deal more configurability. The downside of this is there is more to manage, and more that can go wrong with deployments, etc.