如何创建二维数组目标C

Question

I have 2 arrays that were created dynamically. I have read some examples on the net, and I could not understand it fully. What I see, is that the arrays seems to be 1 Dimension and not 2.

The codes below assigns some objects to array "combineObjectIssues", which will then be added into "combineAll" to get a 2D-Array. I want "currentObject.date" to be index 0, while "issuesDiscovered" array to be index 1.

for (currentObject in currentObjects) {
        [combineObjectIssues addObject:currentObject.date]; //2D Array Row
        for (Issue *checkIssue in currentObject.issuesDiscovered) {
            if (checkIssue) {
                [issuesDiscovered addObject:checkIssue];
            }
        }
        [tempIssues addObject:[issuesDiscovered copy]]; // to combine all array of issues
        [combineOjectIssues addObjectsFromArray:[issuesDiscovered copy]]; //2D Array column
        [combineAll addObject:[combineObjectIssues copy]];
        [issuesDiscovered removeAllObjects]; //remove all objects;
        [combineObjectIssues removeAllObjects]; //remove all objects
    }
}

Below is my output for combineAll array.

(
    (
    "2013-07-19 09:00:00",
    "<Issue: 0x8c171f0>",
    "<Issue: 0x8c16e50>",
    "<Issue: 0x8c16d30>",
    "<Issue: 0x8c16a10>",
    "<Issue: 0x8c16090>",
    "<Issue: 0x8c15bb0>",
    "<Issue: 0x8c156d0>"
),
    (
    "2013-07-13 14:30:00"
),
    (
    "2013-06-08 14:30:00",
    "<Issue: 0x8c10340>",
    "<Issue: 0x8c0fad0>",
    "<Issue: 0x8c0f590>",
    "<Issue: 0x8c0f0c0>"
),
    (
    "2013-05-04 11:30:00"
)
)

As you can see from the output, its a 1 dimension array, which I do not want. I want to have something like, for [0][0], it contains the date, whereby for [0][1], it contains an array of issues.

I know my codes might not be right. As such, kindly assist me. Your assistance(s) are appreciated.

Answer 1

Try this:

you can always get like that values but syntax can be different.

[[combineAll objectAtIndex:0] objectAtIndex:1];

this way you can get the value for [0][1]. you can do like this to make it 2 dimensional array.

also you can do this:

NSString* str = combineAll[0][1];

For all the issue data you can do this:

NSArray* issueArray = combineAll[0];

this will return all the issues at position 0 of combineAll array.

Hope it Helps!!

Answer 2

The question of multidimensional data structures to store Cocoa objects comes up frequently. Sometimes it can be solved by re-thinking your object hierarchy in a way that better fits the conceptual model. But sometimes a multidimensional array is the best mechanism. Ordinary C arrays can store pointers to Cocoa objects, and may be a better way of dealing with this. By way of illustration:

#import <Foundation/Foundation.h>

@interface Foo : NSObject
@property (nonatomic,strong) NSString *name;
@end

@implementation Foo
@end

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        id p[10][10];
        //  create a bunch of foos
        for( uint8_t i = 0; i < 10; i++ ) {
            for( uint8_t j = 0; j < 10 ; j++ ) {
                Foo *aFoo = [[Foo alloc] init];
                aFoo.name = [NSString stringWithFormat:@"Foo_%02d_%02d",i,j];
                p[i][j] = aFoo;
            }
        }
        //  show that we can recover a Foo from C array
        Foo *someFoo = (Foo *)p[5][5];
        NSLog(@"Foo[5][5] = %@",someFoo.name);
        // prints Foo[5][5] = Foo_05_05 to the console
    }
    return 0;
}

Or, if you want to allocate the C array dynamically, you'll have little more work to do. See this gist

Answer 3

You're going to make life hard on yourself by using this kind of data structure. You'll always have to remember that the first index is a different type than the rest of them, and always having to do index shifting and so forth. But if you must, try something like this:

NSMutableArray *output = [NSMutableArray array];
for (YourClass *currentObject in currentObjects) {
    //Making assumption currentObject.issuesDiscovered in an NSArray! if it's not you'll need to initialize the second element differently
    NSArray *arrayForObject = @[currentObject.date,[currentObject.issuesDiscovered copy]];
    [output addObject:arrayForObject];
}