I want to add multiple elements in NSArray with #"title" and value.
for(int i = 0; i < size; i++){
BSDevice *d=[[DeviceManager devices] objectAtIndex:i];
self.dataArray =#[#{#"title":d.Name}];
}
But in this code it only adds one value. When I try with this method it doesn't work:
for(int i = 0; i < size; i++){
BSDevice *d=[[DeviceManager devices] objectAtIndex:i];
[self.dataArray addObject:#[#{#"title":d.buddyName}]];
}
I want to have multiple values with string and its value in NSArray like this #"title":d.Name,#"title":d.Name,#"title":d.Name
Your question isn't very clear and you didn't really explain what problem you are having with the second bit of code, but I think what you want is the following:
for (BSDevice *d in [DeviceManager devices]) {
[self.dataArray addObject:#{ #"title" : d.buddyName }];
}
This assumes that self.dataArray is an NSMutableArray and somewhere before this for loop you initialized self.dataArray as:
self.dataArray = [NSMutableArray array];
I have two codes. Not working is the following:
NSMutableArray *tmpArray = [[NSMutableArray alloc] init];
for (int i=0; i<[dataSetArray count]; i++) {
tmpArray = (NSMutableArray *) [dataSetArray objectAtIndex:i];
// OR use: tmpArray = dataSetArray[i]
... doing stuff
[tmpArray replaceObjectAtIndex:0 withObject:tmpStr];
}
While this works:
for (int i=0; i<[dataSetArray count]; i++) {
NSMutableArray *tmpArray = [[NSMutableArray alloc] initWithArray:[dataSetArray objectAtIndex:i]];
... doing stuff
[tmpArray replaceObjectAtIndex:0 withObject:tmpStr];
}
Two questions:
The first code doesn't yield an NSMutableArray. Why? I declare it
above.
Is there a better way to obtain the same result. I just
dislike defining variables in a loop. This makes the code
unreadable.
--- edit:
Here the full code:
Datatypes are:
dataSetArray: NSMutableArray. However, its contents (i.e. dataSetArray[i]) are NSArrays (I read them into the program from an excel file).
NSString *tmpStr = [[NSString alloc] init];
for (int i=0; i<[dataSetArray count]; i++) {
NSMutableArray *tmpArray = [[NSMutableArray alloc] initWithArray:[dataSetArray objectAtIndex:i]];
for (int j=0; j<[tmpArray count]; j++) {
if ( [dataSetArray[0][j] isEqualToString:#"Number"] ) {continue;}
tmpStr = (NSString *) [tmpArray objectAtIndex:j];
// replace single backslash by double-backslash:
tmpStr = [tmpStr stringByReplacingOccurrencesOfString:#"\\" withString:#"\\\\"];
// replace first dollar sign by "<p>\\[" and second by "\\]</p>"
// Use a methode defined in the NSString+Extension
tmpStr = [tmpStr replaceTexFormulaSigns:tmpStr];
//NSLog(#"j=%d", j);
//NSLog(#"tmpArray is of type: %#", [tmpArray class]);
//NSLog(#" tmpStr is of type: %#", [tmpStr class]);
[tmpArray replaceObjectAtIndex:j withObject:tmpStr];
}
[dataSetArray replaceObjectAtIndex:i withObject:tmpArray];
}
So even if I use your suggestion, I am still facing the same problem with the inner array.
The first code doesn't yield a NSMutableArray. Why? I declare it above.
The declaration of the reference variable tmpArray does not change the type of the referred object. It is still an (immutable) array.
The creation of the mutable array at the very beginning of the first snippet is without any meaning, because the reference to it is overridden.
Is there a better way to obtain the same result. I just dislike defining variables in a loop. This makes the code unreadable.
Yes. The second example works in a way, but do something completely different. (It always creates a new array with a single item in it. No, that's not true. It shouldn't compile at all.)
You should do:
NSMutableArray *tmpArray = [dataSetArray mutableCopy];
for (int i=0; i<[dataSetArray count]; i++)
{
…
[tmpArray replaceObjectAtIndex:i withObject:tmpStr];
}
You should really get some additional knowledge about objects and object references.
How do I initialize an NSArray with size only so to use a for loop to fill it later? My for loop would be
for (int i = 0; i < [myArray count]; i++) {
myArray[i] = someData;
}
You don't need to initialize it with a specific size - you can add objects later:
NSMutableArray *myArray = [NSMutableArray array];
for (int i = 0; i < 100; i++) {
[myArray addObject:someData];
}
There are slight performance gains if you know the size ahead of time:
NSMutableArray *myArray = [NSMutableArray arrayWithCapacity:100];
But this is optional.
NSNull is the class used to represent an unset, invalid or non-existent object. Therefore you can pad the array to a specific size using instances of this class.
NSUInteger sizeOfArray = 10;
NSMutableArray *someArray = [NSMutableArray array];
for (NSUInteger i = 0; i < sizeOfArray; i++) {
[someArray addObject:[NSNull null]];
}
Further, you can't use the syntax someArray[i] = xyz; if the value at position i doesn't exist, as it will cause an out of bounds error.
I have a question about the objective-C. I use the following code to add a contains from an array to another array. However, the second array is null. Can anyone help me? Thank you.
titleArray = [[csvDataArrayString objectAtIndex:0] componentsSeparatedByString:#","];
NSString *title;
dataTitleArray = [[NSMutableArray alloc] init]; // after add this statement it's ok
for(int i=0; i<[tTitleArray count]; i++)
{
title = [csvPersonalTitleArray objectAtIndex:i];
[dataTitleArray addObject:title]; // the dataTitleArray is null
}
You haven't shown that you're actually allocating dataTitleArray anywhere. Are you? It's not clear what you're trying to do.
I used to be a Java Programmer, which the array need to declare the very first time, like this:
int[] anArray; // declares an array of integers
anArray = new int[10]; // allocates memory for 10 integers
I don't know whether the Objective C , NSMutableArray also give me this ability or not. Actually, I want to make a 10*10 array. thz in advance.
I try to do this:
myArray = [[NSMutableArray alloc] initWithCapacity:10];
for (int i=0; i<10; i++) {
myArray[i] = [[NSMutableArray alloc] initWithCapacity:10];
}
But it occurs errors, telling my incompatible type assignment.
The capacity field is seldom useful. The array will be expanded on demand anyway.
And the capacity field just tells the array how much memory you may use. The array's length is still 0.
But you can grow the array from empty:
for (int i = 0; i < 10; ++ i)
[myArray addObject:…];
To read and write to an element in an NSMutableArray, you need:
id x = [array objectAtIndex:i]; // x = array[i];
[array replaceObjectAtIndex:i withObject:y]; // array[i] = y;
You cannot subscript an NSArray directly.
Your code has memory leak. Unlike Java, ObjC doesn't use a GC unless you explicitly enable it (and ObjC on iPhoneOS doesn't have GC). ObjC manages memory by manual reference counting. Basically you need to ensure the ref count of stuff you don't own doesn't change in the process. See http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html for detail.
In your case, [[NSMutableArray alloc] …]; creates an object of ref count +1, then the assignment will take over the array, that means you don't own it any more, but the ref count is not balanced to 0, so this memory will not be properly deallocated. You need to use convenient methods such as [NSMutableArray array…] to create an object with ref count 0.
NSArray's can only store ObjC objects. int in C (ObjC) is a primitive, and cannot be stored into an NSArray. You have to box it into an NSNumber by [NSNumber numberWithInt:0]. You can get back the integer with -intValue.
To conclude, your code needs to be modified as:
-(NSMutableArray*)get10x10Array {
NSMutableArray* arr = [NSMutableArray array];
for (int i = 0; i < 10; ++ i) {
NSMutableArray* subarr = [NSMutableArray array];
for (int j = 0; j < 10; ++ j)
[subarr addObject:[NSNumber numberWithInt:0]];
[arr addObject:subarr];
}
return arr;
}
But ObjC is a superset of C. You can just use a plain 10x10 C array.
int arr[10][10];
You want a 10x10 array -- of what?
myArray = [[NSMutableArray alloc] initWithCapacity:10];
for (int i=0; i<10; i++) {
myArray[i] = [[NSMutableArray alloc] initWithCapacity:10];
}
But it occurs errors, telling my
incompatible type assignment.
Because you can't assign to myArray like that. myArray is an object that represents an array data structure. It is not a C array.
If you want a 10x10 array of a primitive data type, you can declare one like you would in C:
int myArray[10][10];
initWithCapacity: is what you want. It may look like
NSMutableArrat *array = [[NSMutableArray alloc] initWithCapacity:10];
You can't access Cocoa array objects with the bracket notation. Your second bit of code should be:
NSMutableArray *myArray = [[NSmutableArray alloc] initWithCapacity:10];
for (int i = 0; i < 10; i++) {
[myArray insertObject:[NSMutableArray arrayWithCapacity:10] atIndex:i]; // Note: not using myArray[i]!
}
There are two ways to do this.
Plain old C
If you want to store objects, you should use the id type instead of int.
int myarray[10][10];
myarray[5][2] = 412;
Objective-C
NSArray's are not meant to have spaces without objects, if you need them you could use [NSNull null], but if that's the case a C array would be better anyway.
NSMutableArray *myArray = [[NSMutableArray alloc] initWithCapacity:10];
for (int i=0; i < 10; i++) {
NSMutableArray *innerArray = [[NSMutableArray alloc] initWithCapacity:10];
for (int j=0; j < 10; j++) {
[innerArray addObject:[NSNull null]];
}
[myArray addObject:innerArray];
[innerArray release];
}
[[myArray objectAtIndex:5]
replaceObjectAtIndex:2 withObject:[NSNumber numberWithInteger:123]];
NSArray objects have a fixed size that cannot be changed once they have been initialised. NSMutableArray objects can change size. A 10×10 array is sometimes implemented as an NSArray containing 10 individual NSArray objects, each of these containing ten items. This quickly gets cumbersome, sometimes it is easier to resort back to plain C for such a task:
int tenByTen[10][10];
Or, you can use this:
typedef struct
{
int y[10];
} TenInts;
typedef struct
{
TenInts x[10];
} TenByTen;
Then you could do:
- (void) doSomethingWithTenByTen:(const TenByTen) myMatrix
{
NSLog ("%d", myMatrix.x[1].y[5]);
}
And you can also return them from methods:
- (TenByTen) mangleTenByTen:(const TenByTen) input
{
TenByTen result = input;
result.x[1].y[4] = 10000;
return result;
}
You want NSMutableArray +arrayWithCapacity:
Note that setting the initial capacity is merely an optimization - Mutable arrays expand as needed.
EDIT:
To do the 10x10 case,
myArray = [[NSMutableArray alloc] initWithCapacity:10];
for (int i=0; i<10; i++) {
NSMutableArray *subArray = [NSMutableArray arrayWithCapacity:10];
[myArray addObject:subArray];
for (int j = 0; j<10; j++) {
[subArray addObject:[NSNumber numberWithInt:0]];
}
}
Notes:
an array retains the objects added to it, so its not necessary to retain subArray
only objects (not primitive types like "int") can be added to an NSArray, hence the need for NSNumber numberWithInt:
you use methods like objectAtIndex: and replaceObjectAtIndex:withObject: to get/set a value from an NSArray, not array subscript ([]) syntax
See Apple refs for NSArray and NSMutableArray
You can use the following code to resize the NSMutableArray once it was created:
#interface NSMutableArray (Resizing)
- (NSMutableArray *)resize:(NSInteger)newSize;
#end
#implementation NSMutableArray (Resizing)
- (NSMutableArray *)resize:(NSInteger)newSize
{
int size = (newSize > [self count]) ? self.count : newSize;
NSMutableArray *array = [NSMutableArray arrayWithCapacity:size];
for (int i = 0; i < size; i++){
[array addObject:[self objectAtIndex:i]];
}
return array;
}
#end