I would simply like to know how to copy a NSMutableArray so that when I change the array, my reference to it doesn't change. How can I copy an array?
There are multiple ways to do so:
NSArray *newArray = [NSMutableArray arrayWithArray:oldArray];
NSArray *newArray = [[[NSMutableArray alloc] initWithArray:oldArray] autorelease];
NSArray *newArray = [[oldArray mutableCopy] autorelease];
These will all create shallow copies, though.
(Edit: If you're working with ARC, just delete the calls to autorelease.)
For deep copies use this instead:
NSMutableArray *newArray = [[[NSMutableArray alloc] initWithArray:oldArray copyItems:YES] autorelease];
Worth noting: For obvious reasons the latter will require all your array's element objects to implement NSCopying.
Related
I'm try to use the functions -setValue:forKey: and get the value using -valueForKey:
Example:
NSArray *rootarr = [[NSArray alloc] init];
NSArray *array = [[NSArray alloc] initWithObjects:#"name", #"address", #"title", nil];
[rootarr setValue:array forKey:#"n"];
NSArray *getArr = [rootarr valueForKey:#"n"];
But the getArr array I got is not equal the array I set (array).
Could you please tell me what's wrong I met. And what's the way to use these functions?
NSArray's setValue:forKey: method is used for Key Value Coding, not for using an array as an associative container. You need to use NSMutableDictionary.
NSMutableDictionary *rootDict = [NSMutableDictionary dictionary];
NSArray *array = [[NSArray alloc] initWithObjects:#"name", #"address", #"title", nil];
[rootDict setValue:array forKey:#"n"];
NSArray *getArr = [rootDict valueForKey:#"n"];
An array isn't a key-value store, which you appear to want to use it as. I think you want an NSDictionary instead (or more precisely NSMutableDictionary if you want to modify it after its created).
According to the Apple documentation setValue:forKey:
Invokes setValue:forKey: on each of the array's items using the specified value and key.
Practical uses are when you want to set the same value to each element of the array
UILabel *label1 = [[UILabel alloc]init];
UILabel *label2 = [[UILabel alloc]init];
NSArray *arr = #[label1, label2];
[arr setValue:#"bye" forKey:#"text"];
NSLog(#"%# %#",label1.text, label2.text); // bye bye
in your example "getArr" is an empty array because your "rootarr" doesn't have elements, otherwise you receive a setValue:forUndefinedKey: into the contained objects that are not compliant for the assigned key
You can't add objects to an NSArray after it is created. You have to use NSMutableArray in order to do that.
What is the differece between:
[[NSMutableArray alloc] init]
and
[NSMutableArray array]
Here in [NSMutableArray array] you don't have to release array it will be released automatically. & if you will write [NSMutableArray alloc] init] you will have to release array so [[NSMutableArray array] will be equivalent to [[[NSArray alloc] init] autorelease];
The first remains in memory until you release it, the second lasts until the end of the run loop iteration.
NSMutableArray no need to release memory and [NSMutableArray alloc] init] u must be release it.
when ARC does work, you have to release objects come from methods including init,alloc,new,copy and mutableCopy, like [NSMutableArray alloc] init]. If not, the objects will be registered to autoreleasepool, like [NSMutableArray array].
I have an array called addArray which I am adding array objects to:
NSMutableArray *addArray = [NSMutableArray array];
[addArray addObjectsFromArray: delegate.arrayobjectOne];
[addArray addObjectsFromArray: delegate.arrayobjectTwo];
// etc...
Now, if I only want to init one of these arrays to display in my table (preferably from another view controller but that's another question), how would I do this? And how would I access a specific property of each array object, e.g. arrayobjectOne.info?
Thanks for your time.
you can say
someObject = [addArray objectAtIndex: someIndex];
use this Example
NSMutableArray *objectsToAdd= [[NSMutableArray alloc] initWithObjects:#"one",#"two", nil];
NSMutableArray *myArray = [[NSMutableArray alloc] initWithObjects:objectsToAdd,nil];
self.list = [[NSMutableArray alloc] init];
[self.list addObjectsFromArray:myArray];
I want to split string into NSMutableArray
I know
- (NSArray *)componentsSeparatedByString:(NSString *)separator
is available but this one is for NSArray not for NSMutableArray.
I need because after spliting i want to remove element from array by using
-(void)removeObjectAtIndex:(NSUInteger)index
which is not possible with NSArray.
Thank you
You can also just get a mutable copy of the returned array:
NSMutableArray *array = [[myString componentsSeparatedByString:#"..."] mutableCopy];
Also, remember that copy, like alloc, does allocate new memory. So when used in non-ARC code you must autorelease the copied array or manually release it when you are done with it.
Make a new NSMutableArray using
NSArray *array = [NSString componentsSeparatedByString:#"..."];
NSMutableArray *mutable = [NSMutableArray arrayWithArray:array];
Create a NSMutableArray from the output NSArray created by componentsSeparatedByString.
NSMutableArray *mutableArray = [[NSMutableArray alloc] initWithArray:array];
How wouold i do this with a nsmutablearray, its simple with a nsarray just not a mutable array
Thanks
Just create mutable array from non-mutable that you get from that message:
NSMutableArray *mutableComponents = [NSMutableArray arrayWithArray:[yourString componentsSeparatedByString:...]];
The following will work too:
NSMutableArray *mArray = (NSMutableArray *)[yourString
componentsSeparatedByString:#"separator"];
You might need to retain and release when you're done.
Use the following code.
NSArray *array = [someString componentsSeparatedByString:#" "];
NSMutableArray *mutArray = [[NSMutableArray alloc] initWithArray:array];
use the mutArray, this is one NSMutableArray object.