I have an NSMutableArray. It's members eventually become members of an array instance in a class. I want to put the instantiantion of NSMutable into a function and to return an array object. If I can do this, I can make some of my code easier to read. Is this possible?
Here is what I am trying to figure out.
//Definition:
function Objects (float a, float b) {
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:[NSNumber numberWithFloat:a]];
[array addObject:[NSNumber numberWithFloat:b]];
//[release array]; ????????
return array;
}
//Declaration:
Math *operator = [[Math alloc] init];
[operator findSum:Objects(20.0,30.0)];
My code compiles if I instantiate NSMutableArray right before I send the message to the receiver. I know I can have an array argument along with the method. What I have problem seeing is how to use a function and to replace the argument with a function call. Any help is appreciated. I am interested in the concept not in suggestions to replace the findSum method.
Use autorelease to return objects you create in methods/functions.
NSMutableArray* Objects(float a, float b) {
NSMutableArray *array = [[[NSMutableArray alloc] init] autorelease];
// or: [NSMutableArray array];
[array addObject:[NSNumber numberWithFloat:a]];
[array addObject:[NSNumber numberWithFloat:b]];
return array;
}
Or simply:
NSMutableArray* Objects(float a, float b) {
return [NSMutableArray arrayWithObjects:
[NSNumber numberWithFloat:a],
[NSNumber numberWithFloat:b],
nil];
}
Related
I seem to be having a problem with the NSMutableArray.
Here's my code:
NSMutableArray *returnArray = [[NSMutableArray alloc] init];
while(condition) {
NSInteger temp = someNumber;
[returnArray addObject: temp];
}
But as soon as it hits the addObject message, the program seg faults. Any advice?
You can't add primitives like integers to an array, only objects (hence the name addObject:). If you want to add numbers, you have to convert them to an NSNumber, or one of the related classes.
You can only add objects to array and NSInteger is not an array.
NSMutableArray *returnArray = [[NSMutableArray alloc] init];
while(condition) {
[returnArray addObject: [NSNumber numberWithInt: someNumber]];
}
You need to wrap primitives such as NSInteger into an NSNumber class. You can do the following:
while(condition)
{
NSInteger temp = someNumber;
[returnArray addObject:#(temp)];
}
Or if your compiler doesn't support that syntax:
while(condition)
{
NSInteger temp = someNumber;
[returnArray addObject:[NSNumber numberWithInteger:temp]];
}
I'm writing an app for iPhone in objective-c. I want to declare an array that will hold different type of fields , like: int, NSString, bool.
Can I do it?
You can put whatever items in an NSArray as long as they are objects. So you have to wrap items that are not objects (such as BOOL, int and CGPoint) in some kind of objects such as NSNumber or NSValue.
NSMutableArray *array = [[NSMutableArray] alloc] init];
[array addObject:myString];
[array addObject:[NSNumber numberWithInt:1]];
[array addObject:[NSNumber numberWithFloat:1.0]];
[array addObject:[NSValue valueWithPoint:myPoint]]; // myPoint is a CGPoint
[array addObject:[NSValue valueWithRect:myRect]]; // myRect is a CGRect
Yes, you can
NSMutableArray *array = [NSMutableArray array];
NSString *string = #"str";
[array addObject:string]; //string
NSNumber *num = [NSNumber numberWithInt:1];
[array addObject:num]; //int
NSNumber *boolNum = [NSNumber numberWithBool:YES];
[array addObject:boolNum]; //bool
Use NSMutableArray.
NSMutableArray *array = [[NSMutableArray alloc]init];
Now use addObject: method to add objects. for adding int, bool value create NSNumber object.
It is possible. Just create the array and add the objects you want added.
I've created an object, and now I'm trying to create an array full of these objects. I've tried a few different things with no success.
How can I do this?
You can do it one of two ways, with NSArray or NSMutableArray.
id obj1, obj2, obj3;
// This creates a static array
NSArray *array = [NSArray arrayWithObjects: obj1, obj2, obj3, nil];
// This creates a dynamic array
NSMutableArray *mutarray = [NSMutableArray array];
[mutarray addObject:obj1];
[mutarray addObject:obj2];
[mutarray addObject:obj3];
NSMutableArray * arrayOfFoos = [NSMutableArray array];
for (int i = 0; i < 100; ++i) {
Foo * f = [[Foo alloc] init];
[arrayOfFoos addObject:f];
[f release];
}
You can use an NSArray, take a look at Apple's documentation.
If you wanna add them incrementally consider using a mutable collection like an NSMutableArray (here in the doc)
I am trying to create an NSArray of bool values. How many I do this please?
NSArray *array = [[NSArray alloc] init];
array[0] = YES;
this does not work for me.
Thanks
NSArrays are not c-arrays. You cant access the values of an NSArray with array[foo];
But you can use c type arrays inside objective-C without problems.
The Objective-C approach would be:
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:[NSNumber numberWithBool:YES]];
//or
[array addObject:#(NO)];
...
BOOL b = [[array objectAtIndex:0] boolValue];
....
[array release];
EDIT: New versions of clang, the now standard compiler for objective-c, understand Object subscripting. When you use a new version of clang you will be able to use array[0] = #YES
Seems like you've confused c array with objc NSArray. NSArray is more like a list in Java, into which you can add objects, but not values like NSInteger, BOOL, double etc. If you wish to store such values in an NSArray, you first need to create a mutable array:
NSMutableArray* array = [[NSMutableArray alloc] init];
And then add proper object to it (in this case we'll use NSNumber to store your BOOL value):
[array addObject:[NSNumber numberWithBool:yourBoolValue]];
And that's pretty much it! If you wish to access the bool value, just call:
BOOL yourBoolValue = [[array objectAtIndex:0] boolValue];
Cheers,
Pawel
Use [NSNumber numberWithBool: YES] to get an object you can put in the collection.
I want to ask the size of the NSMutable Array can be 2000? If not, is it possible to open an array to store 2000 elements. The elements is the user-defined object. Thank you.
The answer is that an NSMutableArray always starts with a size of zero. If you want it to be so you can do something like this:
NSMutableArray* anArray = [NSMutableArray arrayWithSize: 2000];
[anArray replaceObjectAtIndex: 1999 withObject: foo];
you need to prefill the array with NSNull objects e.g.
#implementation NSArray(MyArrayCategory)
+(NSMutableArray*) arrayWithSize: (NSUInteger) size
{
NSMutableArray* ret = [[NSMutableArray alloc] initWithCapacity: size];
for (size_t i = 0 ; i < size ; i++)
{
[ret addObject: [NSNull null]];
}
return [ret autorelease];
}
#end
Edit: some further clarification:
-initWithCapacity: provides a hint to the run time about how big you think the array might be. The run time is under no obligation to actually allocate that amount of memory straight away.
NSMutableArray* foo = [[NSMutableArray alloc] initWithCapacity: 1000000];
NSLog(#"foo count = %ld", (long) [foo count]);
will log a count of 0.
-initWithCapacity: does not limit the size of an array:
NSMutableArray* foo = [[NSMutableArray alloc] initWithCapacity: 1];
[foo addObject: #"one"];
[foo addObject: #"two"];
doesn't cause an error.