I am currently working on a tile-based-game with numbers in Xcode. In my method called checkGameOver, every tile is moved around to every combination possible, and checked if they are valid moved. However, since that method changes the mutable array called 'values',and I thought the easiest way to avoid this would be to just make a copy of 'values', store it into 'originalValues' and then restore it afterwards. However, it does seem like it actually doesn't change back. I tried using copy also. I don't understand why it doesn't work. Could it be that checkGameOver is really because of the thousands of calculations, and it isn't finished until after the values are changed back?
NSArray *originalValues = [NSMutableArray arrayWithArray:values];
[self checkGameOver];
values = [NSMutableArray arrayWithArray:originalValues];
Explanation: I have array A (values), I create a duplicate of that array, B (originalValues). I make changes on A, but the changes are reflected in B as well.
If you want to make a deep copy of an NSArray, you need to use archiving. See the following example:
NSMutableArray *values = [#[#"one", #"two"] mutableCopy];
NSData *originalValues = [NSKeyedArchiver archivedDataWithRootObject:values];
[values replaceObjectAtIndex:1 withObject:#"something"];
NSLog(#"changed: %#", values);
values = [NSKeyedUnarchiver unarchiveObjectWithData:originalValues];
NSLog(#"restored: %#", values);
Related
I am having hard time with a simple array that i want to pass .
I have a class with some NSMutableArray that i pass to another class(the array is global from singleton)
[mgzm saveWithArray:[Globals sharedGlobals].allImages];
To this function :
-(void)saveWithArray:(NSMutableArray*)currentArray
{
dataToSave=[[NSMutableArray alloc] init]; //local
dataToSave=[currentArray mutableCopy]; //copy
Than i saw that is is changing the original array which i don't want .
So i did this :
dataToSave=[[NSMutableArray alloc] initWithArray:currentArray copyItems:YES];
Which result in a situation that i can't change the dataToSave array get get a crash when trying to.(it needs to be changed).
Than i did this :
for(NSMutableDictionary *dic in currentArray)
[dataToSave addObject:dic];
Which again if i change dataToSave it change also the original array (?! )
Is there a way in this language to COPY array without changing the original one ????
When you make a copy of a mutable array, changing the array copy does not change the original array, not the objects inside the array. Here is what happens when you call [currentArray mutableCopy]:
The two arrays are pointing to the same objects. If you remove an object from the copy, the original array would still have it. However, if you modify the object itself (say, change the name of A to X) the change will reflect on the object in the original array, because it is the same object.
Here is what you want to happen:
Now the two arrays are completely independent of each other. This is the effect that you achieve when you call
dataToSave=[[NSMutableArray alloc] initWithArray:currentArray copyItems:YES];
However, there is a catch: in order for this to work, the objects inside the array must conform to NSCopying protocol, otherwise the code is going to crash.
To fix this, make sure that the objects inside NSMutableArray implement NSCopying. Here is an answer that explains how it is done.
The problem is although you are creating a new array the NSDictionary objects within the new array are still the same ones. So you need to make copies of the NSDictionary objects, you we're close but you need to do something like this...
-(void)saveWithArray:(NSMutableArray*)currentArray
{
dataToSave=[[NSMutableArray alloc] init]; //local
for(NSMutableDictionary *dic in currentArray)
[dataToSave addObject:[NSDictionary dictionaryWithDictionary:dic];
}
I'v run into such problem. I need to update the values in my NSArray. And don't know a way to do it. Here's my array
NSArray *arrayWithInfo = [[NSArray alloc] initWithObjects:AMLocalizedString(#"Status", nil),AMLocalizedString(#"Call", nil),AMLocalizedString(#"Location", nil),AMLocalizedString(#"Control", nil),AMLocalizedString(#"Sim", nil),AMLocalizedString(#"Object", nil),AMLocalizedString(#"Info", nil),nil];
self.dataArray = arrayWithInfo;
[arrayWithInfo release];
To be more specific I have tableview initialized with this array. There is a possibility for user to use different localized strings, so I have to update it. By using [tableview reloadData]; i'v got the table to update, but the values in NSArray stay the same as they were initialized in first place.
So how to make array look up at the strings once again and get their new values?
Use NSMutableArray instead of NSArray
NSMutableArray (and all other classes with Mutable in the name) can be modified.
You should be using an NSMutableArray. Doing so will allow you to change its values after instantiation.
Your array doesn't need to be mutable here as the array seems to be all or nothing. You dont mention the requirement to delete some objects and not others. NSMutableArray isn't needed. You want to write a lazy loading getter method for the array which reinstantiates it if the array doesnt exist.
-(NSArray *)dataArray{
if (_dataArray){
return _dataArray;
}
_dataArray = NSArray *arrayWithInfo = [[NSArray alloc] initWithObjects:AMLocalizedString(#"Status", nil),AMLocalizedString(#"Call", nil),AMLocalizedString(#"Location", nil),AMLocalizedString(#"Control", nil),AMLocalizedString(#"Sim", nil),AMLocalizedString(#"Object", nil),AMLocalizedString(#"Info", nil),nil];
return _dataArray;
}
Then when you want to reload the tableView
self.dataArray = nil;
[tableView reloadData];
this destroys the old array, forcing it to be remade but with the new localisation.
EDIT:
The issue is the array isn't storing the statement AMLocalizedString(#"Status", nil) its storing the result of that statement, which is the localised string itself. There is no way to make the array re-evaluate that statement without either re-creating the whole array again or using an NSMutableArray and changing all the objects. The lazy loading getter method is more in the objective-c style.
You need to use the NSMutableArray. The NSArray is immutable.
I'm trying to set some values to my NSMutableDictionary inside a loop and assigning the dictionary values to an NSMutableArray each time like below,
for(int i=0;i<=lastObj;i++){
[mutableDict setValue:[valuesArray objectAtIndex:i] forKey:#"Name"];
[mutableDict setValue:[uniqueArray objectAtIndex:i] forKey:#"SSN"];
//......then
**[mutableArray addObject:mutableDict];**/*not working perfectly all values s replaced by final mutableDict values (duplicate values)*/
but
**[mutableArray addObject:[mutableDict copy]];**/* Working Correctly !!! */
}
inside loop in each iteration new values is assigned to mutableDictionary and whenever i say just addObject my mutableArray is getting all duplicate values but whenever i say addObject:[mutableDict copy], array is getting correct unique values without any duplicates, i don't know what the difference the compiler feels when i say copy, can anybody tell me the difference in this.
Thanks in advance.
[mutableArray addObject:mutableDict];
keeps on adding mutableDict to mutableArray. adding the object doesnt create a new memory location, it points to the same memory. so when u set the values of mutableDict, it gets reflected in all added objects as they refer to same memory location.
copy creates a new memory location and adds the object removing the above scenario.
to avoid this u can add
for(int i=0;i<=lastObj;i++){
NSMutableDictionary * mutableDict = [NSMutableDictionary new]; //create new memory location
[mutableDict setValue:[valuesArray objectAtIndex:i] forKey:#"Name"];
[mutableDict setValue:[uniqueArray objectAtIndex:i] forKey:#"SSN"];
[mutableArray addObject:mutableDict];
[mutableDict release]; //release
}
hope this helps u. happy coding :)
Looking at your code block, its clear you are allocating mutableDict outside your for loop. Hence When you say below statement inside the for loop, basically you are passing the same object for addition to mutalbeArray.
[mutableArray addObject:mutableDict];
addObject doesnt allocate any memory for objects, but it uses the same object passed and just sends "retain" message to increase the reference count. Since you are passing the same object within the for loop, mutalbeArray would contain the references to same object.
In case of copy say,
[mutableArray addObject:[mutableDict copy]];
the copy message sent to mutableDict returns a new copy which is then passed addObject. Hence every iteration in the forloop passes a new object(due to copy) to addObject.
Also note these following
Copy creates a new object, it should be later released, but your code is not releasing it. This will lead to memory leak.
Copy creates immutable object, hence you should probably use mutableCopy instead if you want objects added to mutableArray to be modified.
I want to maintain a list of records, for each one I maintain the same type of data. I want to use this data in 2 different places:
UITableView that takes from each record the "Name" value
UIViewController that takes all the data to use in different fields.
I assume I should be using a plist to store the data; I also assume that the object that should be receiving the data for the UITableView is NSArray so I can use the cellForRowAtIndexPath method to create the table automatically.
So i created the plist "PLForArr.plist":
It seems that i can only get a NSDictionary when calling the plist using
NSString *path = [[NSBundle mainBundle] pathForResource:#"PLForArr" ofType:#"plist"];
NSArray * myArr = [[NSArray alloc] initWithContentsOfFile:path]; //doesn't work...
NSDictionary * myDict = [[NSDictionary alloc] initWithContentsOfFile:path]; //does work, but who to I make a NSArray out of it / or get the data from here to the UITableView?
I understand that i don't understand something basic here... Can someone take me step by step on:
How to keep the data - should I use plist or something else? Should I have a main record of type array (as I did on the example plist here) or can I just keep it as these Dictionaries without the unnecessary MyArr that I used considering the UITableView end target?
How to call the data - Is there a way to get it into a NSArray or must it get into a NSDictionary?
How to call it into the the UITableView - Can I fill in the lines using a NSDictionary?
Storing the data is an Array or a Dictionary is up to you. But if you want to make changes to it over time you can't store it in the main bundle.
Your pList file is a dictionary that contains an array. See code example below.
You will have to store the dictionary in an array for the data source for your table. See code example below.
Assuming that your UITableView's data source is called tableArray. You can use tableArray to fill in the information in the table and your view. Oh yeah,
NSString *path = [[NSBundle mainBundle] pathForResource:#"PLForArr" ofType:#"plist"];
NSDictionary *myDict = [[NSDictionary alloc] initWithContentsOfFile:path];
NSArray *myArray = [myDict objectForKey:#"MyArray"];
self.tableArray = [myArray copy];
[myArray release];
[myDict release];
This goes in tableView: cellForRowAtIndexPath:
cell.text = [[tableArray objectAtIndex:row]objectForKey:#"Obj Name"];
Storing your data either in a dictionary, or in an array is up to you. Depending on the kind of data you have, you will consider storing unordered collection of objects (dictionary), accessing the entries with keys; or rather in ordered collection (array), using numeric indexes.
It's fine to get arrays from property list files, but the root (top level) object is a dictionary (in the screenshot, "MyArr" isn't the top-level object, it is the key for accessing your array in the top-level dictionary). To get your array from it, simply alloc/init the plist dictionary the way you did, and access the array entry using its key ([myDict objectForKey:#"MyArr"]). Otherwise make sure you set the root object of the property list to be an array, and retry NSArray's initWithContentsOfFile:
The real question seems to be How can I fill the cells with my data ? The table views ask its delegate and dataSource about how many sections, rows in a section, to display. Based on these numbers, it will ask the dataSource for cells. Once again depending on the storage type you've chosen, you will implements these methods a little bit differently, but the concepts remain.
You will probably want to read documentation about :
Property List
Table views
When should I use copy instead of using retain? I didn't quite get it.
You would use copy when you want to guarantee the state of the object.
NSMutableString *mutString = [NSMutableString stringWithString:#"ABC"];
NSString *b = [mutString retain];
[mutString appendString:#"Test"];
At this point b was just messed up by the 3rd line there.
NSMutableString *mutString = [NSMutableString stringWithString:#"ABC"];
NSString *b = [mutString copy];
[mutString appendString:#"Test"];
In this case b is the original string, and isn't modified by the 3rd line.
This applies for all mutable types.
retain : It is done on the created object, and it just increase the reference count.
copy -- It creates a new object and when new object is created retain count will be 1.
Hope this may help you.
Copy is useful when you do not want the value that you receive to get changed without you knowing. For example if you have a property that is an NSString and you rely on that string not changing once it is set then you need to use copy. Otherwise someone can pass you an NSMutableString and change the value which will in turn change the underlying value of your NSString. The same thing goes with an NSArray and NSMutableArray except copy on an array just copies all the pointer references to a new array but will prevent entries from being removed and added.