I'm quite confused on how to add objects in multidimensional arrays.
Is initializing multidimensional arrays are the same with just a simple array?
This is my initialization.
testList = [[NSMutableArray alloc] init];
I need to do something like
testList[i][j] = item;
i tried
[[[testList objectAtIndex:i]objectAtIndex:j] addObject:item];
but it doesn't seem to work :(
You are add to much C to do this. This is important to know how to NSMutableArray works and how it's different compare to 2D arrays known from C/C++.
In mutable array you could store another arrays. For example:
NSMutableArray *first = [[NSMutableArray alloc] init];
NSMutableArray *second = [[NSMutableArray alloc] init];
[first addObject:second];
Now you have array in first row in first array! This is something very like C/C++ 2D arrays.
So if you want to add some object to "0,0" you do this:
NSString *mytest = [[NSString alloc] initWithString:@"test"];
[second addObject:mytest];
[first addObject:second];
So now your second contains NSStrings and first contains second. Now you can loop this like you want.
----EDIT: IF you want 1,0 you simply need another instance of second NSMutableArray. For example you have this array:
So here you will be have 3 elements in second array.
NSMutableArray *first = [[NSMutableArray alloc] init];
for(int i =0 ; i < your_size_condition ; i++) {//if you have size, if don't not a problem, you could use while!
NSArray *second = [[NSArray alloc] initWithObjects:"@something",@"somethingelse",@"more",nil];
[first addObject:second];
}
You may want to implement NSCopying protocol to do this.
If you need a fixed size array, then use plain C array. Before using dynamic ObjC array it needs to create it:
NSMutableArray* array = [NSMutableArray arrayWithCapacity:N];
for(int i=0; i<N; i++) {
[array addObject:[NSMutableArray arrayWithCapacity:M]];
}
UPD: The following methods might be helpful to work with such array:
[[array objectAtIndex:i] addObject:obj];
[[array objectAtIndex:i] insertObject:obj atIndex:j];
[[array objectAtIndex:i] replaceObjectAtIndex:j withObject:obj];
To expand upon @onegray's answer, you can set up some category methods to make soft multidimensional arrays easier to deal with.
MultiMutableArray.h
@interface NSMutableArray(MultiMutableArray)
-(id)objectAtIndex:(int)i subIndex:(int)s;
-(void)addObject:(id)o toIndex:(int)i;
@end
@implementation NSMutableArray(MultiMutableArray)
MultiMutableArray.m
#import "MultiMutableArray.h"
-(id)objectAtIndex:(int)i subIndex:(int)s
{
id subArray = [self objectAtIndex:i];
return [subArray isKindOfClass:NSArray.class] ? [subArray objectAtIndex:s] : nil;
}
-(void)addObject:(id)o toIndex:(int)i
{
while(self.count <= i)
[self addObject:NSMutableArray.new];
NSMutableArray* subArray = [self objectAtIndex:i];
[subArray addObject: o];
}
@end
example, MultiArrayTests.m
#import <SenTestingKit/SenTestingKit.h>
#import "MultiMutableArray.h"
@interface MultiArrayTests : SenTestCase
@end
@implementation MultiArrayTests
-(void)testMultiArray
{
NSMutableArray* a = NSMutableArray.new;
[a addObject:@"0a" toIndex:0];
[a addObject:@"0b" toIndex:0];
[a addObject:@"0c" toIndex:0];
[a addObject:@"1a" toIndex:1];
[a addObject:@"1b" toIndex:1];
[a addObject:@"2a" toIndex:2];
STAssertEquals(a.count, 3U, nil);
NSMutableArray* a1 = [a objectAtIndex:0];
NSMutableArray* a2 = [a objectAtIndex:1];
NSMutableArray* a3 = [a objectAtIndex:2];
STAssertEquals(a1.count, 3U, nil);
STAssertEquals(a2.count, 2U, nil);
STAssertEquals(a3.count, 1U, nil);
}
@end
I have written further details at http://peterdeweese.tumblr.com/post/27411932460/soft-multi-dimensional-arrays-in-objective-c
[[testList objectAtIndex:i] insertObject:item atIndex:j];
NSMutableArray(orNSArray) objects to your originaltestList, because there is no multi dimension array in objective-c; you could use theNSMutableDictionary(orNSDictionary) with KVC; or you could combined them with each other; or you could useNSMutableSet(orNSSet) or you could combine everything with everything... everything is highly limitless, it depends on what kind of data you'd like to represent.