I need to show some data in a textview coming from coredata (like this for example),
I imagine a possible solution (dont know if is the right one or how to do it, please advice),
so bring the data from coredata to a string, appending all the data neeeded in the string with the equivalent of "\n" for new line where needed; then show the data in the text view,
(please refer to example image to know what is needed)
so how to bring the data from coredata to this textView with this formatting?
please note I only want to know if this is a proper way to do it (imagined solution? or if there is a more proper way?)
Thanks a lot!!
I tackled an identical issue in one of my apps.
The approach I took was to first structure my core data model so that the pieces of data had enough granularity so that I could construct different views as required. In other words, instead of one property for "name", I have three properties. One for "first name", one for "middle name", and a third for "last name". I also created a separate "data layer" object so that I could easily get to pieces of my data from anywhere in the app.
Next, to construct my view that shows data in a sort of form view. Using Interface Builder, I simply laid out a view using primarily UILabel view objects as placeholders. Then, as the user switches between person views, I call on the data layer object for pieces of data and just "fill in" in the UILabel placeholders.
I also render a PDF file in paragraph form. Similar to what you are doing. For that, I use an NSMutableString along with the NSString stringWithFormat convenience method. Using NSMutableString, you can concatenate strings with newline characters embedded as needed. For this, I also call on my data layer object for the pieces of data.
[[NSString stringWithFormat:#"Date of Visit: %#", dateOfVisitString] drawInRect:stringRect withFont:theFont];
Hope this helps. Good Luck.
Yes, your strategy of
'bring the data from coredata to a
string, appending all the data neeeded
in the string with the equivalent of
"\n" for new line where needed; then
show the data in the text view'
will work fine.
(Bit of an odd answer, but it seems to be what you're asking, from your comment clarification.)
Your approach is fine. If you're targeting a textview for display, then constructing a formatted string from a managed object's properties is reasonable. Use NSMutableString and its -appendFormat: method.
You may also want to explore creating a report form out of UILabels laid out inside a UIView. Interface Builder would be the tool to use for this, but you could also create this in code.
Related
I am drawing a tableview via BehaviorRelay.
Currently, I am using the code below as a way to add data.
viewModel.user.append(Person(name: "king", phoneNumber: "12341234"))
viewModel.personObservable.accept(viewModel.user)
I wonder if this code changes the user itself so that the whole tableView is redrawn.
If so, what method can I use to change only the data I added?
The code presented causes the personObservable (which is actually a BehaviorRelay apparently,) to emit a next event that contains an entire array of Person values, not just the latest Person added. Importantly, it's not emitting the viewModel.user object (at least not conceptually) but an entirely different object that happens to be equal to viewModel.user.
The default dataSource, the one that you get when you call items with anything other than a DataSource object, will call reloadData on the table view. This doesn't cause "the whole tableView" to be redrawn though, but it will cause the table view to query the data source for all of the visible cells, even if they haven't changed.
If you only want the table view to load the new cell, then the data source object needs to be smart enough to compare the new array with the array it's currently displaying so it can figure out which values are different and add/remove/move cells as appropriate, instead of just calling reloadData. As #Sweeper said in the comments, the RxDataSources library contains a set of data source classes that have that logic built in. If you wanted to reinvent the wheel, just write a class that conforms to both RxTableViewDataSourceType & UITableViewDataSource and implement the diffing yourself.
I'm a new developer creating a simple "dictionary" app for personal use and my question is about how to properly implement the Model-View-Controller design in my particular situation. Please bear with me for the necessary background:
I want to be able to hit a button and have a label display a word on one side of the screen, and to have another label display a list of associated words on the other side.
For instance: when I hit the button I want the main label to display "cats" and for the list to display "tiger", "snow leopard", "lion", etc. The output would be random: the label displayed would be random and the list would be scrambled.
I've achieved this output in the Xcode 4.3 console through storing each list in an NSMutableArray, and using an NSDictionary to hold all of the NSArrays. Here is the code:
//creates lists
NSArray *catList = [NSArray arrayWithObjects:#"Lion", #"Snow Leopard", #"Cheetah", nil];
NSArray *dogList = [NSArray arrayWithObjects:#"Dachshund", #"Pitt Bull", #"Pug", nil];
...
//creates dictionary and stores lists values with dictionary keys
NSMutableDictionary *wordDictionary = [[NSMutableDictionary alloc] init];
[wordDictionary setObject: catList forKey:#"Cats"];
[wordDictionary setObject: dogList forKey:#"Dogs"];
...
//randomizes selection of dictionary key
NSInteger keyCount = [[wordDictionary allKeys] count];
NSInteger randomKeyIndex = arc4random() % keyCount;
//displays selected key, which is the main word
NSLog(#"%#", randomKey);
//selects array list corresponding to key
NSMutableArray *randomlySelectedArray = [wordDictionary objectForKey:randomKey];
//shuffles the output of the selected word list array
for( int index = 0; index < keyCount; index++ )
{
int randomIndex = arc4random() % keyCount;
[randomlySelectedArray exchangeObjectAtIndex:index withObjectAtIndex:randomIndex];
}
//prints word list and removes displayed dictionary selection
NSLog(#"%#", randomlySelectedArray);
[wordDictionary removeObjectForKey:randomKey];
(I need to add code that does displays a main word and list one at a time, maybe using NSTimer, but this is what I've got so far.)
Using a single-view template in Xcode, I've been able to get the simulator to show a main word and a corresponding list by adding some of this code to the IBAction method of the button in my view controller implementation file. (Of course I changed NSLog to initWithFormat.) However, none of my randomization code works.
My question, finally, is how do I separate things so that they conform best to the MVC design? I'm thinking that: My button and my two labels constitute the view. My view controller is the controller, and my NSArrays and NSDictionary data are the Model.
However, I've been keeping all of my model data inside the view controller, which I'm pretty sure is wrong. I think that I need to figure out how to create a class for my NSArrays and NSDictionary to store my model data. Then I must manage to get my button & labels to display the desired text of my model data via my view controller. At least I think that's how MVC works.
I'm wondering if that understanding is correct and if anyone has any pointers on how to organize my model data most effectively to get my desired output.
Thanks very much for any help! I'm stuck!
Before starting to design an application based on MVC. We first need to know what these different components are and what MVC help us to achieve?
Why we use MVC?(Model-View-Controller)
Because it helps us in:
Separating responsibilites also leads to reusability
By minimizing dependencies, you can take a model or view class you’ve already written and use it elsewhere
Think of ways to write less code
While designing an application based on MVC, we should focus on above points.
Lets relate this 'Dictionary' application with real world dictionary.
A dictionary is composed of words, their meaning, pronunciation, examples, usage, antonyms, synonyms, indexes and other similar information.
When a user wants to look for a particular word he will use top-margin word for fast look-up. Once he found the right page he will go to that word and see its meaning, usage or other needed information.
Model Part:
Lets draw analogy between your application and what I described above.
In your application you will be having a class : 'Dictionary' which
will represent the real world dictionary. This dictionary is composed
of words, their meaning, pronunciation, usage and other information.
So we will need an array of words which will contain 'Word' object.
The 'Word' class will have all the information that we wish to provide
for particular word. You can also provide other attributes that you
can think of that belongs to Dictionary and add them to it.(Here we are talking about content only)
Now we need to think of different operations to be performed on this dictionary. The most basic operation are creating a dictionary and accessing it.
We will have a DictionaryCreator class which will add all the words that our dictionary will have. So this is another class
'DictionaryCreator'. Or we can put this creating logic in 'Dictionary'
init methods. But it will be helpful to have this class this will
enable the dictionary add-word features.
Once DictionaryCreator creates a dictionary, User will be ready to use it. So we will need to provide different operations that a user
can perform on 'Dictionary' as its methods. In our case we can
consider user is over controller, which in fact is controlled by real
user.
The above techique will help you to create a component that performs only its responsiblity and can be reused in other application or extended for future use.
*Always remember Model is the most reusable component of MVC design. So whenever you are in doubt about Model just go remind the words 'Model must be reusable'.
(Not aware of views or controllers)
So we have just finished Model part of the application.
View Part:
This depends on you, what interface you wish to provide to user. But lets again consider the real world Dictionary. A real world dictionary's content(information) is spread across several pages. This view helps us to view/access/mark/bookmark in dictionary.(Remember that here user performs all the operation and not the pages neither the dictionary). The pages have easy look-up word on top or bottom and some pronunciation guidance at bottom.
In your application you said "I want to be able to hit a button and have a label display a word on one side of the screen, and to have another label display a list of associated words on the other side."
Here we have again have multiple options to implement this, you can create view using Interface Builder and connection them with your controller. But then again this controller and View will be tightly coupled and when we wish to use similar interface somewhere else we will be unable to do so. So for reusability we will create another UIView class and create it with a new View XIB and load this nib. So in future if you need similar kind of view you can easily reuse(like cocoa-touch provides us UIView, UIButton etc.).
*View also tends to be a reusable component in MVC.
(Not aware of controllers, may be aware of relevant model objects)
Controller Part:
Now we have created view and model but how will they communicate? Controller will help them in this. A controller :
Knows about model and view objects
The brains of the operation
Manages relationships and data flow
Typically app-specific, so rarely reusable
*The points and definition I have taken from Stanford University Lectures[CS193P - Lecture 6
iPhone Application Development
Designing iPhone Applications Model-View-Controller (Why and How?) View Controllers]
Update:
Recently, I have come across another good lecture on MVC. It explains this design concept in much better way with very nice examples. It is available at iTunes U or you can directly go to first lecture by iPad and iPhone Application Development (SD) by Paul Hegarty.
How does look the practical usage of IBOutletCollection? Unfortunately Apple documentation mentions it briefly without giving an wider idea of usage. OK, it maintains one-to-many relation with IB, but how to access and use particular objects efficiently? With TagName? How to ensure the order of objects?
I've recently used this to easily initialize a grid of labels. I have a n by n matrix of labels on a view, and reference each one individually (via an IBOutlet) in order to display relevant data. However when the view first loads I wanted to control the default text that displayed in all the labels. Initially i wanted a dash to display, but since this is for a client I wanted it to be easy to change. The view contents have and continue to change over time, per client requests.
Instead of writing N line of code, I created an IBOutletCollection and accomplished the same results in 4 (#property, #synthesize, and for loop). YMMV but I found it very useful in this situation.
Read again this section in the Interface Builder User Guide.
IBOutletCollections are actually just NSArrays you can connect to more than one object in IB. All the objects you connected end up in this array and can be accessed from code like any other object in an array.
I used it to minimize code. I have a range of UIViews that should react on "touch up inside" events of some UIButtons (custom mode).
I gave all UIButtons a tag (lets say 1005 to 1010) and all UIViews the same tag as the UIButton they shall respond to.
Then I connected the UIViews with the collection in Interface Builder. All UIButton touch up events go to the same function in my controller. This function gets the tag of the sender object, iterates through the NSArray list (of "IBOutletCollection(UIView)") and compares the tag. Everytime it hits, the appropriate action is done.
It is a pity that NSArrays seem not to hold the order...
I apologise if this has been asked before but I can't find the info I need.
Basically I want a UITableView to be populated using info from a server, similar to the SeismicXML example. I have the parser as a separate object, is it correct to alloc, init an instance of that parser & then tell RootViewController to make it's table data source a copy of the parser's array.
I can't include code because I haven't written anything yet, I'm just trying to get the design right before I start. Perhaps something like:
xmlParser = [[XMLParser alloc] init];
[xmlParser getXMLData];
// Assuming xmlParser stores results in an array called returnedArray
self.tableDataSource = xmlParser.returnedArray
Is this the best way of doing it?
No, you don't want to do this. You don't want your view controller directly accessing the array of the data-model. This would work in the technical sense but it would be fragile and likely to fail as the project scaled.
As the projects grow in complexity, you will want to increasingly wrap your data model object (in this case the xmlParser) in protective layers of methods to control and verify how the data model changes. Eventually, you will have projects with multiple views, multiple view controllers as well as information entering from both the user and URLs. You need to get into the habit of using the data-model object not just a dumb store you dump stuff into but as an active manager and verifier of your data.
In a situation like this I would have my data-model's array completely wrapped by making it a #protected or #private property. Then I would have dedicated methods for fetching or inserting data into the actual array inside the data-model class itself. No objects outside of the data-model should actually have direct access to the array or have knowledge of its indexes.
So, in this case your data-model would have something like:
- (NSString *) textForLineAtIndexPath:(NSIndexPath *) anIndexPath{
//... do bounds checking for the index
NSString *returnString=[self.privateArray objectAtIndex:anIndexPath.row];
if (returnString=='sometest'){
return returnString;
}
return #""; //return an empty string so the reciever won't nil out and crash
}
as well as a setTextForLineAtPath: method for setting the line if you need that.
The general instructional materials do not spend enough (usually none) time talking about the data-model but the data-model is actually the core of the program. It is where the actual logic of the application resides and therefore it should be one of the most complex and thoroughly tested class in your project.
A good data-model should be interface agnostic i.e. it should work with a view based interface, a web based interface or even the command line. It should neither know nor care that its data will be displayed in a tableview or any other interface element or type.
When I start a new project, the first thing I do is comment out the '[window makeKeyAndVisible];' in the app delegate. Then I create my data-model class and test it old-school by loading data and logging the outputs. Only when it works exactly how I wish it to do I then proceed to the user interface.
So, think real hard about what you want the app to do on an abstract level. Encode that logic in a custom class. Isolate the data from all direct manipulation from any other object. Verify all inputs to the data before committing.
It sounds like a lot of work and it is. It feels like overkill for a small project and in many cases it is. However, getting the habit early will pay big dividends very quickly as your apps grow in complexity.
Not quite. You want the data source to be an object that implements the UITableViewDataSource protocol; what I would do in this situation is create an object that implements that protocol and parses XML, so that you can alloc-init it, then set the data source to that object and have it update the table view as appropriate. So based off your code (and assuming you're running within the table view's controller):
XMLParserAndDataSource xpads = [[XMLParserAndDataSource alloc] init];
[xpads getXMLData];
self.tableView.dataSource = xpads;
It's probably a good idea to give this class itself a reference to an NSXMLParser object, so you can use that to parse the XML, then provide convenience methods (like getXMLData) as well as the UITableViewDataSource methods for your own use. (If you go this route, you should also make your XMLParserAndDataSource class implement the more useful of the NSXMLParser delegate methods, and use them as appropriate to update your table view.)
I'm a Mac programmer and not an iPhone programmer; but on the mac,
self.tableDataSource = xmlParser.returnedArray is not correct. You are supposed to either bind the table's content to an Array Controller (if iPhone has one?) or set the datasource outlet to your RootViewController.
In your rootview controller, you would implement the methods:
– tableView:cellForRowAtIndexPath:
– tableView:numberOfRowsInSection:
For – tableView:cellForRowAtIndexPath: you would return a UITableViewCell with the data you received from the XML parsing according to the index path like so:
UITableCell *myCell = [UITableCell new];
myCell.textLabel.text = [parsedXMLArray objectAtIndex:[indexPath indexAtPosition:indexPath.length-1]];
return myCell;
(Something people don't know is that you can use the + new class method on all NSObject subclasses which automatically call alloc/init.)
For – tableView:numberOfRowsInSection just return the count of the data array:
return parsedXMLArray.count;
Can't edit my question nor post replies, can only post my response as answer.
#TechZen: I'm somebody who tries to form analogies, helps me understand. What you're saying is something like: My original idea was like going into the file room & dumping all the originals on my desk to work on where as you suggest the object be more like an organised file clerk who will search through the data for me and only return the specific datum that I need while being the only one with direct access to that data.
Have I understood correctly?
#Tim: What if I later need the parser to get data for something which is not a table? That's why I thought to dump it into an array & let the caller decide what to do with the data. Would you suggest a second object that would supply the data in the newly required form? (Am I sort of one the right track here or way off?)
My app is made up of a TabBarController, each tab with a UITableView.
On launch I parse an XML file from my server into an Object class and then display the objects in the first tableview.
My question is, what do I do when I want to parse a second XML file? Currently, when doing so, the information in "XML-file-2" will overwrite the objects parsed by "XML-file-1". How do I go about this properly? Do I set up another Object class for each XML file or is there another to work around the issue?
I am using NSXMLParser.
I think you should consider having two instances of XMLParser, one for each XML file you want to read. It allows you to read as many XML files concurrently without affecting each other. It is also more modular.
on line 21 of that snippet ( http://pastie.org/537227 ) you are setting the products array (appDelegate.products)to a new mutable array. if you want the second run to append to appDelegate.products, you should see if appDelegate.products already has objects in it, if so, don't assign a new array to it, just add to them to it using NSMutableArray's addObject: method
... Don't overwrite the data that's already there...?
If you're displaying the contents in a UITableView, then I'd be willing to bet you've got an NSArray in there somewhere. Hopefully, if you've set this up properly, the NSArray contains model objects, each one of which corresponds to one row in your UITableView. However, I would suggest using NSMutableArray. Then when you parse the second XML file and build your model objects out of that, just use NSMutableArray's addObject: method and then reloadData on the UITableView.
As notnoop already mentioned, to make multiple NSXMLParser instances would be the best solution.
A open source iPhone RSS reader called Simple RSS Reader would be a good sample of what you want now.
You might use RSSParser class of the Simple RSS Reader as it is.
HTH