Is there any patters that I can use to understand if my data model has changed to original state.
Let's see at situation when I have an object Order which can include some price info, items number, order notes info and etc. So at start it's an empty order and if I will update any properties by adding something new I will need to detect that the model exactly changed.
So let's say I put 5 items number at start and save data mode of Order. Then I want to update this model by putting 2 new items then KVO or any other tool should tell me about updates in data model, but if I set 5 items number one more time (like NSInteger itemNumbers = 5) so it means I triggered setter of the property, but I have not modified original value.
Related
I'm trying to clear an array after each iteration of a for loop in LabVIEW, but the way I've implemented it has the values not going directly to what I want, but it changes with previous values in other parts of the array.
It isn't shown, but this code is inside of a for-loop that iterates through another numeric array.
I know that if I get the array to clear properly after each loop iteration, this should work. How do I do that? I'm a beginner at Labview but have been coding for awhile - help is appreciated!!!
[![labview add to array][2]][2]
It looks as if you're not quite used to how LabVIEW passes data around yet. There's no need to use lots of value property nodes for the same control or indicator within one structure; if you want to use the same data in more than one place, just branch the wire. Perhaps you're thinking that a LabVIEW control or indicator is equivalent to a variable in text languages, and you need to use a property node to get or set it. Instead, think of the wire as the variable. If you want to pass the output of one operation to the input of another, just wire the output to the input.
The indicators with terminals inside your loop will be updated with new values every loop iteration, and the code inside the loop should execute faster than a human can read those values, so once the loop has finished all the outputs except the final values will be lost. Is that what you intended, or do you want to accumulate or store them in some way?
I can see that in each loop iteration you're reading two values from a config file, and the section is specified by the string value of one element of the numeric array Array. You're displaying the two values in the indicators PICKERING and SUBUNIT. If you can describe in words (or pseudocode, or a text language you're used to) what manipulation of data you're actually trying to do in the rest of this code, we may be able to make more specific suggestions.
First of all, I'm assuming that the desired order of operations is the following:
Putting the value of Pickering into Array 2
Extracting from Array 2 the values to put in Pickering 1 and Pickering 2
Putting Array 2 back to its original value
If this is the case, with your current code you can't be sure that operation 1 will be executed be fore operation 2. In fact, the order of these operations can't be pre-determined. You must force the dataflow, for example by creating a sequence structure. You will put the code related to 1 in the first frame, then code related to operation 2 in the second.
Then, to put Array 2 back to it's original value I would add a third frame, where you force an empty array into the Value property node of Array 2 (the tool you use for pickering, but as input and not as output).
The sequence structure has to be inside the for loop.
I have never used the property node Reinit to default, so I can't help you with that.
Unfortunately I can't run Labview on this PC but I hope my explanation was clear enough, if not tell me and I will try to be more specific.
I was wondering what kind of data I can use to handle a dataChanged-signal in a QML ListModel.
I found out that it has three arguments, two of which are QModelIndices and one is a QVariant(...).
So from the first two (which seems to be the same?) I can get the row, column (which is supposed to be 0), the model itself and uhm... stuff
But why do I get it twice?
And what is the content of the third? It is not null, but I haven't found a property I could use to retrieve some useful data from it.
A ListModel implementsQAbstractItemModel, the dataChanged signal you are seeing is the one defined in this class :
void QAbstractItemModel::dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles = QVector<int> ())
The 2 first parameters tell us that all data between the first and second indexes are changed. The 3rd parameter is a list of roles where the data has changed, if the list is empty it means the data at all roles has potentially been changed.
In your case the first and second indexes are the same because only one row is changed at a time.
I am wondering if its possible to have a core data and use a NSFetchedResultsController to display template holders; without saving the placeholder template holder to core data.
I am writing an app where a table view will have the following characteristics
Maximum amount of rows (ie: 8)
Each cell uses a partial view, a single table cell instance with clickable buttons;
A user clicking on the buttons replaces the content for each button
When a user comes to save the data it stores the content in the exact places, but crucially it should not save the blank placeholder state; but still respect the placement positioning.
IE: Lets say a user picks the right button for cell 1 and saves it;
when the the user returns to this dataset sometime in the future, it
should have the imagery and data in the correct place; but still keep
the left button for cell 1 empty (placeholder)
The reason I don't want to save the placeholder content is because I consider this data to be "dirty"; its meaningless and has no place in a dataset; its a view; not data.
Currently:
I create data using insertInManagedObjectContext but do not save it until the user has pressed save.
Each matchRow has many fighters. This relationship is a NSOrderedSet, managed by core data.
The problems I'm having are;
NSFetchedResultsController only respects saved core data items; and ignores the placeholder data.
If a user only saves one (right button) data, the NSOrderedSet sees this as the first (left button) data; which is in correct
If I strip out all the placeholder structures from the core data in a pre-save action, the effect is that the order the user wanted is now lost and it causes a crash when reloading because the size of the arrays are incorrect.
Currently the only way around this is to stop using
NSFetchedResultsController and use a NSArray; and put the placeholders into the array too, then save everything, (dirty objects) and all.
I really don't want to do that. The placeholder content isn't meant to be saved.
I've been reading a blog post on using separate classes for special cases where he has different data sources; and uses the technique to separate class for the "empty" case, and to set it as the table view’s datasource when it's empty.
Whilst this is interesting, it only solves it for an empty case; when my requirement is that the partial view should handle all states; empty data and partial data.
One idea I have is that we need another entity between our record and our match rows;
Match - MatchRowMeta - Fighter
Not sure what the relationship would be
where;
RowMeta {
record.obj (relationship)
fighters.obj (relationship)
positionID (integer) - which button has been set
}
But I don't think this is the best way to do it; it seems expensive and a lot of heavy lifting to do something relatively simple.
Thus, my question:
Is it possible to have a table view made up of template holders; where the structure is saved to core data but none of the empty (dirty) objects are saved; plus NSFetchedResultsController will respect the structure; even when its empty or partially empty?
Edit: Added entity diagram
I would like to make some bindings that toggle item titles in a popup menu based on a single numerical value in a text field. Let me explain:
This is my UI:
I want my menu items to automatically adjust to singular or plural based on the number in the text field. For example, when I type "1" in the box, I want the menu items to be labeled "minute", "hour" and "day". When I type "4", I want the menu items to be labeled "minutes", "hours" and "days".
What I did to date:
I bound the three menu item's labels to the same key path as the text field's value.
I created an NSValueTransformer subclass to interpret the value in the text field and return singular or plural to be used as item titles.
I applied this value transformer to the three bindings.
The issue:
My value transformer can either return singular or plural but it can't set the appropriate string based on the menu item it's applied to.
It looks to me like a value transformer is generic and can't return different values for different destinations. That would mean that to have the three titles change automatically, I would need to have three different value transformers that return the appropriate string for each menu item. That doesn't seem optimal at all.
Ideally I would be able to combine a string stored in the destination menu item (let's say in the item's tag property) with an "s" in the value transformer when the text field's value is larger than one, or something similar that would enable me to use a single value transformer for all the menu items.
Is there something I missed? What would be an ideal solution?
Okay, this is probably not an ideal solution, but something you could consider: if you set your value transformers from your code (and not in IB), you could instantiate 3 different transformers of the same class. You could give your value transformer an ivar NSString *unit (and add something like [[MyValueTransformer alloc] initWithUnit:]) to allow each to return their own string, but you still have to write the value transformer's code only once.
(Also, if you're ever going to consider making your application localizable, simply appending an "s" to create the plurals is not going to work. You could of course add ivars for both NSString *singular and NSString *plural to do that.)
Edit: Wait, I just realized you can register value transformers! If you register them as MyValueTransformerHours and MyValueTransformerMinutes (by manually allocating and initializing them in your code), you can use them from Interface Builder. See also https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ValueTransformers/Concepts/Registration.html#//apple_ref/doc/uid/20002166-BAJEAIEE.
I'm new here at stackoverflow :) But I think, this is the right place to ask my question.
I'm a new developer with Cocoa and Objective-c & I'm trying to write my first App for Mac: a ToDo App.
At this moment, i can save ToDo's and delete them, but now, I want to add some features like CreationDate, some Tags (in mutablearray), and if the ToDo is finished or not. Im not working with an ArrayController, I'm saving the encoded NSMutableArray into a File (Library/Application Support/AppName) and reading it from there.
This all must be in one Row, because it is looking Like this:
Current appearance http://img683.imageshack.us/img683/7595/bild2ss.png
Where Title is, should be the Content of the ToDo, where the Blue Box is, should be the Status (Blue = undone, Grey = Done) and where Subtitle is should be the Date and the Tags (03.01.2009 - tag1, tag2, tag3)
I now how to addObjects into an mutablearray but, if i wanna save all this 4 informations into this array, i dont know how to make this.
I've got an Model, which is initializing with this 4 infomations, but how to save this? Must I save this for informations in one array and this array in my mutablearray?
The solution is actually the opposite: Have one object per row.
This is where your model layer (the M in MVC) comes in: The object for each row is a model object, an instance of a class you construct, and the icon, title, and subtitle are properties of that object.
Then, make a custom cell for your table column to display the model object in that way. The cell is part of the View layer—the V in MVC.
The C in MVC sits in between the Model and View: It's the object that owns the model and is the data source (whether by Bindings or not) of the table view. The table view gets the model objects from this object to feed them to the cell. This middle object is a Controller.
Now i have it!
I've only one Cell for the Content with an ArrayController.
I'm setting the other Informations with -(id)init for each row.
There are 3 Objects: content, status and date, and for each status i display another image (done, undone, ...).
Thank you very much for your Help! I'm trying to finish the Beta for everyone :)