Basically my view controller has 49 different instance variables of class CircleView (called circleView1, circleView2, ..., circleView49). The CircleView class is a simple subclass of UIImageView and basically returns a circle picture when initialized.
Here is what I am trying to do:
In my implementation for the view controller, I want to be able to select the instance variable using a string, for example let's say I generate a random integer i between 1 and 49, lets say it's 5. I would like to be able to build an NSString using something like [NSString stringWithFormat #"circleView%i",i]; and somehow reach the actual circleView5 instance variable. Is this possible?
P.S. I'm looking for something in the lines of NSClassFromString, but which applies to instance variables or objects.
KVC is your friend. Assuming you have a string with the name of the circleView in it,
NSString *myCircle = [NSString stringWithFormat:#"circleView%i", i];
you access that property on the controller using KVC:
CircleView *theCircle = [self valueForKey:myCircle];
On a side note, you should consider redesigning the object heirarchary; this will be very difficult to maintain, and there are certainly better ways to do it (an array with the CircleView's accessed by index would be my first choice).
Instead of having a pile of variables and trying to access them via a string, use an array (either a primitive C array or an NSArray: I'll demo with an NSMutableArray). Declare a NSMutableArray *circleViews; in your class like you did the circleViewN instances. In your initializer, instead of a bunch of circleViewN = [[CircleView alloc] init];, you'd have something like:
circleViews = [NSMutableArray arrayWithCapacity:50];
for(int i=0; i<50; i++)
[circleViews addObject:[[[CircleView alloc] init] autorelease]];
Then you can access the desired circle with your random int i with [circleViews objectAtIndex:i];.
Related
I have an NSDictionary that I am passing to a NSObject Class where I pull all of the values out of the dictionary and pass them into their correct types.
For instance NSInteger, BOOL, NSString, char are the types of values I am pulling out of the NSDictionary and putting into their only variables.
My question what is the best way to turn these values into one big object that can then be putt into an array?
I have heard that I can use the class itself as an Object.. But I am not really sure how to do this.
or could I just put them back into a NSDictionary?... but if thats the case do NSDictionaries allow for multiple value types?
Actually, you are in the right path. this is basically MVC architecture way. so you are questioning about M = Model.
Model in here example is class that defines all variables. cut to the point, here's you should do:
-> create a class that contain your variable, with #property & #synthesize name : ClassA.
then you could set object ClassA into dictionary.
ClassA *myClass = [[ClassA alloc] init];
myClass.myString = #"test String";
myClass.myBoolean = True;
[dictionary setObject:myClass forKey:#"myObject"];
[myClass release]; //we no longer need the object because already retain in dictionary.
then retrieve it by :
ClassA *myClass = (ClassA*)[dictionary objectForKey:#"myObject"];
NSLog(#"this is value of myString : %# & boolean : %i",myClass.myString,myClass.myBoolean);
You can put the collection of values in NSDictionary, NSArray, NSMutableArray, etc. Any of the collection types. Or if you have a fixed number of values/types, you can create a class that has a data member for each value/type and put it in that. The class solution would eliminate having to do a lot of casting, but it also only works if there are a fixed number of values/types.
Here is the AppleDoc on collections.
Yeah, You can create a class itself with these as different values as a properties.Once you pass this object to any class you can access those values there by obj.propertyName.Doing by this Lead to create Modal in MVC pattern.
Please let me know if there is doubt.
Test *object = [[Test alloc] init];
object.testBool=true;
object.testString=#"Test";
NSDictionary *passData = [[NSDictionary alloc] initWithObjectsAndKeys:object,#"testObject", nil];
Test *getObject = (Test*)[passData objectForKey:#"testObject"];
NSLog(#"%d",getObject.testBool);
NSLog(#"%#",getObject.testString);
You can customized the init method of Test Class.
I know I can concatenate a variable name using stringwithformat, but is it possible to concatenate an object name? I'm not having any luck working around this one.
image+1.hidden = YES; for example.
If I wanted to loop through that, say 10 times, how would I create the 'image+1' part?
Thanks for any help.
I don't think that it is possible to concatenate object names in objective c, but you could create an array of images, and then reference each image like
image[0].hidden = YES;
That would fit the for loop. You could also add the images (I assume that they are UIImages) to an NSArray, then loop through like so:
NSArray* arrayOfImages;
for(UIImage* image in arrayOfImages)
{
image.hidden = YES;
}
Add the objects to an NSArray or NSMutableArray. Then loop through the array to set each object's properties.
For the purposes of discussion mainly, you can use key-value coding to set a property by its name. So, supposing you had instance, an instance of a class that provides the properties image1, image2 and image3 then you could perform:
for(int x = 1; x < 4; x++)
{
// produce the name of the property as an NSString
NSString *propertyName = [NSString stringWithFormat:#"image%d", x];
// use key-value coding to set the property
[instance setValue:someValue forKey:propertyName];
}
For the full list of accessor methods that compliant classes export, see the NSKeyValueCoding Protocol Reference. NSObject implements NSKeyValueCoding, and all properties declared as #property and implemented as #synthesize are compliant, as are any other properties with suitable accessors.
As already noted in the other answers, when what you want is an ordered list of objects so that you can do something with each in turn, either a C-style array or an NSArray is the correct way to proceed, with an NSArray being preferred for style reasons.
NSArray *array = [[NSArray alloc] initWithObjects:image1, image2, image3, image4, image5, image6, image7, image8, image9, image10, nil]; // or use NSMutableArray
for (int x = 0; x < 10; x++) {
((UIImage*)[array objectAtIndex:x]).hidden = YES;
}
The data source for my table view is a plain NSMutableArray that will be populated as the app runs, but will be empty when the Table View first loads. The class interface looks like this...
#interface ViewController_iPhone : UITableViewController {
NSMutableArray *serverList;
}
#property (retain, readonly) NSMutableArray *serverList;
#end
My questions are...
Currently, I initialize it in the viewDidLoad method like so...
serverList = [[NSMutableArray alloc] initWithCapacity:1];
I do it this way because the array needs to be valid in order for my numberOfRowsInSection method to avoid crashing when reading the count of the array (which will be zero) when the view first loads. My current approach of using initWithCapacity just feels a little clunky since I just need an empty, but valid array object that will return a count value of zero when the view loads. How should I be initializing my serverList array?
While playing around, I noticed that when I try and initialize the serverList array this way...
serverList = [NSMutableArray arrayWithCapacity:1];
it crashes on that line. Why?
Thanks in advance for all your help!
Here's a key concept to learn about member variables and properties: Member variables are not the same as properties.
That is, when accessing a member variable in your class:
serverList = [NSArray array]; is not the same as self.serverList = [NSArray array];
serverList by itself means you're accessing it directly.
self.serverList means you're using the getter/setter methods to access it.
Normally this isn't that big of a deal when dealing with basic variable types. However, when your property uses retain or copy, that means your setter method will automatically retain it when you use it, but it won't do such when you access it directly.
That means:
serverList = [NSArray array]; will not retain the array.
self.serverList = [NSArray array]; will retain the array.
It should be noted that [NSMutableArray arrayWithCapacity:1]; (and 99% of other methods that aren't alloc) will return an object that is autoreleased. If you want to keep it for later use, as you need to in this case, then you must retain it in some form or fashion.
I somehow missed the simplest approach and found that when I simply create the array like so...
serverList = [[NSMutableArray alloc] init];
and release it in the dealloc method, everything works great!
Note that capacity does not mean any objects are in the array. Using -initWithCapacity: simply sets aside a chunk of space for the array. Nothing is in the array even with a non-zero capacity.
The following initializers:
self.serverList = [[[NSMutableArray alloc] init] autorelease];
self.serverList = [[[NSMutableArray alloc] initWithCapacity:capacity] autorelease];
self.serverList = [NSMutableArray array];
self.serverList = [NSMutableArray arrayWithCapacity:capacity];
should all work, however.
Make sure you specify self so that the property is accessed. Using serverList by itself will not work.
Make sure you autorelease any alloc-init of a property which you are retaining, otherwise you will have a memory leak.
You do not need an array with a specified capacity. This is just a performance convenience for setting aside contiguous memory, and useful if you have a rough idea how much space your array will need up-front. An array that is created through alloc-init will also be empty, with a count of zero.
I have a custom class of type NSObject that contains a single NSMutableArray. This class is called Mutable2DArray and is designed to emulate a 2 dimensional array of type NSMutableArray. There is a custom init method - (id)initWithX:(int)x Y:(int)y that asks for the dimensions for the array and allocates the required arrays within the only array the class owns.
My issue is when I try to copy an instance of Mutable2DArray I get an error saying the copyWithZone is an unrecognized selector. I thought copy was a base method of NSObject so I'm confused why I cant create a copy of the instance like this:
Mutable2DArray *Array1 = [[Mutable2DArray alloc] initWithX:10 Y:10];
Mutable2DArray *Array2 = [Array1 copy];
Am I missing something so obvious here?
Things that I can think of to check, off the top of my head:
Does the header file actually declare the interface as inheriting from NSObject?
Does your custom initWithX: Y: method call [super init] before finishing?
The reason I'm asking this is because right now I use an NSMutableSet of integers and a corresponding NSMutableArray to store the rest of the data, but I think I'm not using the language right. Here's my code:
In the init function:
self.markerList = [[NSMutableArray alloc] init];
self.markerIdSet = [[NSMutableSet alloc] init];
And the function that updates the set and array:
- (void) addMarker: (RMMarker*)marker AtLatLong:(CLLocationCoordinate2D)point {
if (![self.markerIdSet member: [node objectForKey:#"id"]]) {
[self.markerIdSet addObject:[node objectForKey:#"id"]];
[self.markerList addObject:marker];
}
}
I would be a bit wary of having a mutable object as part of a key in a set as if the object changes its hash code etc could change but the set would not know about it ( unless you make the addMarker remve the object and then add it back with the new hash code)
However in your example can't you just use a dictionary (or am I missing something?)
self.markerDict = [[NSMutableDictionary alloc]init];
- (void) addMarker: (RMMarker*)marker AtLatLong:(CLLocationCoordinate2D)point {
if ([nil != [self.markerDict [node objectForKey:#"id"]]) {
[self.markerDict setValue:marker forKey:[node objectForKey:#"id"]];
}
}
The NSMutableSet contains unique elements. Uniqueness is determined by the hash and isEquals methods, so in order to do what you want, you should either subclass or delegate an NSMutableDictionary and in your own concrete class implement these methods so that the specific key you require is the equality and hash factor.
Don't make an NSMutableSet of NSMutableDictionary directly; make a custom class that has an NSMutableDictionary property. This custom class should implement -isEqual: and -hash in terms of your id—i.e. this object will be equal to another object if the ids are equal, and two objects with the same id will have the same hash.
More documentation with regard to -isEqual: and -hash.