sorry for the simple question but how do you make a CAlayers using a for loop?
I have this now but what is the proper way of doing this?
for (int n = 1; n <= 6; n++) {
NSString *theCloud = [NSString stringWithFormat:#"cloudImage%d",n];
NSString *theCloudLayer = [NSString stringWithFormat:#"cloudLayer%d",n];
CALayer *theCloudLayer = theCloud.layer;
}
any help is appreciated.
Use an NSArray or NSMutableArray, not a bunch of variables with numbers at the end of their names (also known as a Poor Man's Array).
So that would be something like:
NSArray *cloudImages; // Use this to store your objects currently in the cloudLayerN variables
NSMutableArray *cloudLayers = [NSMutableArray array];
for (id cloud in cloudImages) {
[cloudLayers addObject:[cloud layer]];
}
Related
I have an array like this:
array: (
(
"http://aaa/product/8_1371121323.png",
"http://aaa/product/14_1371123271.png"
),
(
"http://aaa/product/9_1371121377.png"
)
)
and I have to create another array from that one like this
array: (
"http://aaa/product/8_1371121323.png",
"http://aaa/product/14_1371123271.png",
"http://aaa/product/9_1371121377.png"
)
How can I do that? Is it possible to combine all the objects and separate them using some string?
It can be done in a single line if you like key-value coding (KVC). The #unionOfArrays collection operator does exactly what you are looking for.
You may have encountered KVC before in predicates, bindings and similar places, but it can also be called in normal Objective-C code like this:
NSArray *flatArray = [array valueForKeyPath: #"#unionOfArrays.self"];
There are other collection operators in KVC, all prefixed with an # sign, as discussed here.
Sample Code :
NSMutableArray *mainArray = [[NSMutableArray alloc] init];
for (int i = 0; i < bigArray.count ; i++)
{
[mainArray addObjectsFromArray:[bigArray objectAtIndex:i]];
}
NSLog(#"mainArray :: %#",mainArray);
Sample code:
NSArray* arrays = #(#(#"http://aaa/product/8_1371121323.png",#"http://aaa/product/14_1371123271.png"),#(#"http://aaa/product/9_1371121377.png"));
NSMutableArray* flatArray = [NSMutableArray array];
for (NSArray* innerArray in arrays) {
[flatArray addObjectsFromArray:innerArray];
}
NSLog(#"%#",[flatArray componentsJoinedByString:#","]);
NSMutableArray *arr1 = [NSMutableArray arrayWithArray:[initialArray objectAtIndex:0]];
[arr1 addObjectsFromArray:[initialArray objectAtIndex:1]];
Now arr1 contains all the objects
I have a variable name referencing question for the Objective C gurus out there.
Lets say I have 6 UILabels on a form, the are setup with properties naming them myLabel1 - myLabel6
I would like to go through a for loop and populate these with something depending on the loop but im unsure how to specifiy the for loops variable and make it part of the labels name.
Here is what I would like to do:
for (int LP = 0; i <5)
{
labelLP.text = [NSString stringWithFormat:#"My label number:%d", LP};
}
What im not sure of is how to reference the label and append the LP int and use it in my loop. I'm sure there is a way to do this just not sure how.. Anyone??
you can always take advantage of the dynamic runtime of objective-c:
id var = object_getIvar(self,class_getInstanceVariable([self class], [[NSString stringWithFormat:#"label%d",LP] UTF8String]));
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html
Whether one likes this approach is a question of style, but here's a way that should work:
for (int LP = 1; i <=6)
{
NSString *labelName = [NSString stringWithFormat: #"label%d", i];
UILabel *labelLP = (UILabel*)[self valueForKey: labelName];
labelLP.text = [NSString stringWithFormat:#"My label number:%d", LP};
}
I don't think you can create variable names on the fly, at least not trivially.
You could always use a switch case inside your loop:
for (int i=0; i<5; i++) {
switch(i) {
case 1:
myLabel1.text = [NSString stringWithFormat:#"My label number: %d", i];
break;
case 2:
myLabel2.text = [NSString stringWithFormat:#"My label number: %d", i];
break;
...
...
}
}
You could also store your labels in an array, and loop through that array.
The important point is not to get fixated about the variable names, but to think about why you need your objects and how to get them.
I am very new to Objective-C with Cocoa, and I need help.
I have a for statement in which I loop i from 1 to 18, and I would like to add an object to an NSMutableArray in this loop. Right now I have:
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++)
{
[chapterList addObject:#"Chapter"+ i];
}
I would like it to add the objects, chapter 1, chapter 2, chapter 3... , chapter 18. I have no idea how to do this, or even if it is possible. Is there a better way? Please Help
Thanks in advance,
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++)
{
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d",i]];
}
good luck
Try:
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d", i]];
In Objective-C/Cocoa you can't append to a string using the + operator. You either have to use things like stringWithFormat: to build the complete string that you want, or things like stringByAppendingString: to append data to an existing string. The NSString reference might be a useful place to start.
If you're wanting strings that merely say Chapter 1, Chapter 2, you can just do this:
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++) {
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d",i]];
}
And don't forget to release the array when you're done, as you're calling alloc on it.
I'm a beginner in Objective-C and I'm trying to find the most convenient way to work with multidimensional arrays in Objective-C. Either I am missing something or they are very ugly to work with.
Let's say we have a classic problem:
read input from file; on the first line, separated by space(" ") are the width and height of the matrix (eg: 3 4)
on the following lines there is the content described by the values above
Eg:
3 4
a b c d
e f g h
i j k l
The first solution I thought of was:
NSMutableArray *matrix = [[NSMutableArray alloc] initWithCapacity: x]; //x = 3 in this specific case
NSMutableArray *cell;
for(cell in matrix)
{
cell = [NSMutableArray initWithCapacity: y];
for(int i = 0; i < y; i++) // y = 4
{
//object is a NSString containing the char[i][j] read from the file
[cell insertObject:object atIndex: i];
}
}
This was the first thing I had in mind when thinking about how I should get my values read from file in a multidimensional array. I know you can use C arrays, but since I will store NSObjects in it, I don't think is such a great idea. Nonetheless, from my point of view is easy to work with C arrays rather the solution I got with Objective-C.
Is there another way you could build a multidimensional array in obj-c and easier than the one above?
How about looping them?
I know I can do something like
NSArray *myArray;
for(int i=0; i < [array count]; i++)
{
[myArray arrayWithArray: [array objectAtIndex: i]];
for(int j=0; j < [myArray count]; j++)
{
NSLog(#"array cell [%d,%d]: %s", i, i, [myArray objectAtIndex: j]);
}
}
But that is still more complicated than your average C multidimensional array loop.
Any thoughts on this?
Objective-C is a superset of C, if you want to work with multidimensional arrays like you would in C, do it that way. If you want to work with objects doing it the Cocoa way, then that's fine too, but you will write more code to do it.
Can you not simply make an array of id?
#import <Foundation/Foundation.h>
int main(int argc, char **argv) {
id ptr[3][4];
NSObject *p;
ptr[0][0] = p;
}
You can do nothing more with NSArray or NSMutableArray in this regard. That is there is nothing like objectAtIndex:i :j
You can always create one-dimensional arrays of the size width * height instead:
const int size = width*height;
NSMutableArray *array = [NSMutableArray arrayWithCapacity:size];
for (int i=0; i<size; ++i) {
NSString *string = [NSString stringWithFormat:#"col=%d, row=%d", i%width, i/width];
[array insertObject:string atIndex:i];
}
Nobody uses direct multi-dimensional arrays of any size in any computer language (except for homework). They simply use too much memory and are therefore too slow. Objective-C is an object-oriented language. Build a class that does what you need.
I want to ask about the objective C question. I want to create a 2D NSArray or NSMutableArray in objective C. What should I do? The object stored in the array is NSString *. Thank you very mcuh.
This is certainly possible, but i think it's worthy to note that NSArrays can only hold objects, not primitive types.
The way to get around this is to use the primitive wrapper type NSNumber.
NSMutableArray *outer = [[NSMutableArray alloc] init];
NSMutableArray *inner = [[NSMutableArray alloc] init];
[inner addObject:[NSNumber numberWithInt:someInt]];
[outer addObject:inner];
[inner release];
//do something with outer here...
//clean up
[outer release];
Try NSMutableDictionary with NSNumbers as keys and arrays as objects. One dimension will be the keys, the other one will be the objects.
To create the specific "2D array"
NSMutableDictionary *twoDArray = [NSMutableDictionary dictionary];
for (int i = 0; i < 10; i++){
[twoDArray setObject:arrayOfStrings forKey:[NSNumber numberWithInt:i]];
}
To pull the data
NSString *string = [[twoDArray objectForKey:[NSNumber numberWithInt:3]] objectAtIndex:5];
//will pull string from row 3 column 5 -> as an example
Edited to make my answer more applicable to the question. Initially I didn't notice that you were looking for a 2D array. If you know how many by how many you need up front you can interleave the data and have a stride. I know that there are probably other (more objective standard) ways of having arrays inside of an array but to me that gets confusing. An array inside of an array is not a 2 dimensional array. It's just a second dimension in ONE of the objects. You'd have to add an array to each object, and that's not what I think of as a 2 dimensional array. Right or wrong I usually do things in a way that makes sense to me.
So lets say you need a 6x6 array:
int arrayStride=6;
int arrayDepth=6;
NSMutableArray *newArray = [[NSMutableArray alloc] initWithCapacity:arrayStride*arrayDepth];
I prefer to initialize the array by filling it up with objects;
for(int i=0; i<arrayStride*arrayDepth; i++) [newArray addObject #"whatever"];
Then after that you can access objects by firstDim + secondDim*6
int firstDim = 4;
int secondDim = 2;
NSString *nextString = [newArray objectAtIndex:firstDim+secondDim*6];