Alright, I'm having the following common problem
[NSCFNumber isEqualToString:]: unrecognized selector sent to instance
but this time I'm not sure how to fix it.
Here's the declaration in viewDidLoad:
- (void)viewDidLoad {
[super viewDidLoad];
NSMutableArray *tempHours = [NSMutableArray array];
for (int i = 0; i < 12; i++) {
[tempHours addObject:[NSNumber numberWithInt:(i+1)]];
}
self.hours = tempHours; // 'hours' is a synthesized NSArray property of the ViewController
[tempHours release];
// two more similar array declarations here
}
Here's the code method of the UIPickerView where stuff breaks (e.g., the if statement)
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
NSString *stringIndex = [NSString stringWithFormat:#"Row #%d", row];
if(component == 0) {
return stringIndex = [self.hours objectAtIndex:row];
}
// more code for other components (of the same form) here
return stringIndex;
}
I think I need my NSArray of NSNumber objects to be type-casted as strings. How do I do that properly with that statement:
stringIndex = [self.hours objectAtIndex:row];
Thanks!
return [NSString stringWithFormat:#"%#",[self.hours objectAtIndex:row]];
You are returning an NSNumber as that is what is held in self.hours. As NSString is the expected return value you should create a string via:
[NSString stringWithFormat:#"%#", [self.hours objectAtIndex:row]];
or reevaluate your intent. Did you actually want to store indices in this way, or did you want to store NSStrings?
If anyone is having this problem and specifically returning an index of a row, then you can always convert the NSNumber to a stringValue by doing the following:
NSString *code = [[[JSONResponse objectForKey:#"meta"] objectForKey:#"code"] stringValue];
Placing a stringValue at the end of the method will convert anything to a string, you can also use intValue.
Comment [tempHours release];//it is autoreleased object. You didn't use and with alloc or copy or new:
- (void)viewDidLoad {
[super viewDidLoad];
NSMutableArray *tempHours = [NSMutableArray array];
for (int i = 0; i < 12; i++) {
[tempHours addObject:[NSNumber numberWithInt:(i+1)]];
}
self.hours = tempHours; // 'hours' is a synthesized NSArray property of the ViewController
// [tempHours release];
}
more over u have added NSNumber to array
so
convert to string value:
stringIndex =[NSString stringWithFormat:#"%#",[self.hours objectAtIndex:row]];
Related
I am new to Objective C and I'm having trouble getting my head around a few things.
I am trying to make a big integer program, from which I read items entered in a string and put them into an individual elements in the array.
I am currently working on an add method which adds elements from both the arrays together to make a big number stored in a final array.
But I'm kind of confused about to get this array I made from the initWithString method into the array method. I have some understanding of self, but I don't really know how to use it in this sense.
#implementation MPInteger
{
}
-(id) initWithString: (NSString *) x
{
self = [super init];
if (self) {
NSMutableArray *intString = [NSMutableArray array];
for (int i = 0; i < [x length]; i++) {
NSString *ch = [x substringWithRange:NSMakeRange(i, 1)];
[intString addObject:ch];
}
}
return self;
}
-(NSString *) description
{
return self.description;
}
-(MPInteger *) add: (MPInteger *) x
{
//NSMutableArray *arr1 = [NSMutableArray arrayWithCapacity:100];
//NSMutableArray *arr2 = [NSMutableArray arrayWithCapacity:100];
//for (int i=0; i < 100; i++) {
//int r = arc4random_uniform(1000);
//NSNumber *n = [NSNumber numberWithInteger:r];
//[arr1 addObject:n];
//[arr2 addObject:n];
// }
self.array = [NSMutableArray initialize];
return x;
}
#end
int main(int argc, const char * argv[]) {
#autoreleasepool {
MPInteger *x = [[MPInteger alloc] initWithString:#"123456789"];
MPInteger *y = [[MPInteger alloc] initWithString:#"123456789"];
[x add: y];
}
}
So I want too add the x and y arrays, but I'm not sure how to get the arrays in the add method. Do I use self to represent one of the arrays and initialise it, and x to represent the other. I don't know if I'm going about it completely the wrong way. Some help to understand would be greatly appreciated.
When referring to self you're actually accessing the current instance of the class. In other languages this may be implemented as this instead. There are a couple ways of designing the approach you're going for but the simplest pattern is probably composition:
#interface MPInteger
{
NSMutableArray *digits;
}
#end
----------------------------------------------------------------------------
#implementation MPInteger
-(id) initWithString: (NSString *) x
{
// Create a new instance of this class (MPInteger) with a default
// constructor and assign it to the current instance (self).
self = [super init];
if (self) {
// Previously we initialized a string, but then threw it out!
// Instead, let's save it to our string representation:
self->digits = [NSMutableArray array];
for (int i = 0; i < [x length]; i++) {
NSString *ch = [x substringWithRange:NSMakeRange(i, 1)];
[self->digits addObject:ch];
}
return self;
}
// Depending on how you want to implement this function, it could return
// a new MPInteger class or update the current instance (self):
-(MPInteger *) add: (MPInteger *) x
{
NSArray *a = self->digits;
NSArray *b = x->digits;
// Have both strings for A + B, so use them to find C:
NSArray *c = ????;
// Return a new instance of MPInteger with the result:
return [ [ MPInteger alloc ] initWithString:c ];
}
#end
Notice that now the MPInteger class has an instance of an NSString object that will exist during the entire lifetime of the MPInteger object. To update/access this string, all you need to do is say:
self->digits
I need a method that would add a few objects (2-10) to my array, skipping these that are nils:
NSMutableArray *arr = [[NSMutableArray alloc] init];
[arr addObjectsSkipNils:obj1, obj2, obj3];
How I can write this method in an elegant way?
This category method would work:
#interface NSMutableArray (MyAdditions)
- (void)addObjectsSkipNilsWithCount:(NSUInteger)count objects:(id)obj, ...;
#end
#implementation NSMutableArray (MyAdditions)
- (void)addObjectsSkipNilsWithCount:(NSUInteger)count objects:(id)obj, ...
{
va_list ap;
va_start(ap, obj);
// First object:
if (obj != nil)
[self addObject:obj];
// Remaining objects:
for (NSUInteger i = 1; i < count; i++) {
id myobj = va_arg(ap, id);
if (myobj != nil)
[self addObject:myobj];
}
va_end(ap);
}
#end
Example:
NSMutableArray *a = [NSMutableArray array];
[a addObjectsSkipNilsWithCount:3 objects:#"foo", nil, #"bar"];
NSLog(#"%#", a);
// Output: ( foo, bar )
You have to specify the number of objects explicitly, because nil cannot be used as terminator for the variable argument list. (And bad things can happen if the count is greater than the actual number of objects supplied !)
You can use:
[yourMainArray removeObjectIdenticalTo:[NSNull null]];
Now if you want to copy this to arr you can do quite easily.
How can I create array of floating point numbers in Objective-C?
Is it possible?
You can create a dynamic array (size decided at runtime, not compile time) in different ways, depending on the language you wish to use:
Objective-C
NSArray *array = [[NSArray alloc] initWithObjects:
[NSNumber numberWithFloat:1.0f],
[NSNumber numberWithFloat:2.0f],
[NSNumber numberWithFloat:3.0f],
nil];
...
[array release]; // If you aren't using ARC
or, if you want to change it after creating it, use an NSMutableArray:
NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:0];
[array addObject:[NSNumber numberWithFloat:1.0f]];
[array addObject:[NSNumber numberWithFloat:2.0f]];
[array addObject:[NSNumber numberWithFloat:3.0f]];
...
[array replaceObjectAtIndex:1 withObject:[NSNumber numberWithFloat:99.9f]];
...
[array release]; // If you aren't using ARC
Or using the new-ish Objective-C literals syntax:
NSArray *array = #[ #1.0f, #2.0f, #3.0f ];
...
[array release]; // If you aren't using ARC
C
float *array = (float *)malloc(sizeof(float) * 3);
array[0] = 1.0f;
array[1] = 2.0f;
array[2] = 3.0f;
...
free(array);
C++ / Objective-C++
std::vector<float> array;
array[0] = 1.0f;
array[1] = 2.0f;
array[2] = 3.0f;
For an dynamic approach you can use NSNumber object and add it to NSMutableArray, or if you need only static array then use suggestions from comments, or use standard C.
like:
NSMutableArray *yourArray = [NSMutableArray array];
float yourFloat = 5.55;
NSNumber *yourFloatNumber = [NSNumer numberWithFloat:yourFloat];
[yourArray addObject:yourFloatNumber];
and then to retrive:
NSNumber *yourFloatNumber = [yourArray objectAtIndex:0]
float yourFloat = [yourFloatNumber floatValue];
If you are using Xcode 4.4+, you can try this:
NSArray *a = #[ #1.1f, #2.2f, #3.3f];
Here is all new literals of LLVM Compiler 4.0.
How about something like this?
#interface DoubleArray : NSObject
#property(readonly, nonatomic) NSUInteger count;
#property(readonly, nonatomic) double *buffer;
- (instancetype)init NS_UNAVAILABLE;
- (instancetype)initWithCount:(NSUInteger)count NS_DESIGNATED_INITIALIZER;
- (double)valueAtIndex:(NSUInteger)idx;
- (void)setValue:(double)value atIndex:(NSUInteger)idx;
#end
#implementation DoubleArray
- (void)dealloc
{
if (_buffer != 0) {
free(_buffer);
}
}
- (instancetype)initWithCount:(NSUInteger)count
{
self = [super init];
if (self) {
_count = count;
_buffer = calloc(rows * columns, sizeof(double));
}
return self;
}
- (double)valueAtIndex:(NSUInteger)idx
{
return *(_buffer + idx);
}
- (void)setValue:(double)value atIndex:(NSUInteger)idx
{
*(_buffer + idx) = value;
}
#end
It's a basic array. You can extend this with more complex features like appending, indexed removal etc.
When I Build & Run my application, it will not generate anything. What I have generating are words and after it erases that word and continues until it exhausts all the words and then repopulates the list again. Here is the code:
#implementation randomnumbersViewController
#synthesize words;
#synthesize randomArray;
#synthesize array;
-(IBAction)generateNumber:(id)sender {
NSInteger randomize(id num1, id num2, void *context);
int rand = arc4random() %2;
if (rand)
return NSOrderedAscending;
else
return NSOrderedDescending;
}
- (void)resetRandomArray;
{
[randomArray setArray: array];
[randomArray sortUsingFunction:random context:NULL];
}
- (NSString*) getRandomWord; {
if ([randomArray count] ==0)
return nil;
NSString* result;
NSInteger randomIndex = [[randomArray lastObject] intValue];
[randomArray removeLastObject];
result = [words objectAtIndex:randomIndex];
return result;
}
- (void)buildRandomWordArray
{
NSInteger index;
NSError *theError;
NSString *path = [[NSBundle mainBundle] pathForResource:#"words" ofType:#"text"];
NSString *text = [NSString stringWithContentsOfFile: path
encoding: NSUTF8StringEncoding
error: &theError];
self.words = [text componentsSeparatedByString: #"\n"];
int arraySize = [words count];
self.array = [NSMutableArray arrayWithCapacity:arraySize];
//This code fills "array' with index values from 0 to the number of elements in the "words" array.
for (index = 0; index<arraySize; index++)
[array addObject: [NSNumber numberWithInt: index]];
[self resetRandomArray];
//for (index = 0; index<=arraySize; index++)
// NSLog(# "Random word: %#", [self getRandomWord]);
}
Also a .txt document must be included in the resources folder in for this to work and I do have it there, but nothing. Does anyone have any suggestions as to how I can actually get it to generate the words, or why it isn't working properly?
I don't get how sorting the array ascending or descending is going to shuffle the array, maybe because it doesn't. :) You should use the Fisher–Yates shuffle implemented here: What's the Best Way to Shuffle an NSMutableArray? Import that category, and just call shuffle on the mutable array.
Okay, so, I'm doing a simple lookup. I have an array of NSString objects and a string to search for in the array's elements.
It all seems to work up until I try to add a match to a new mutable array made to hold the search results. The stringHolder variable gets the string, and resultsCollectorArray even get the right number of new elements, but each element is empty and "out of range". Here's the method:
#implementation NSArray (checkForString)
-(NSMutableArray *) checkForString: (NSString *) matchSought
{
long unsigned numberofArrayElements;
long unsigned loop = 0;
NSRange searchResults;
NSMutableArray * resultCollectorArray = [[NSMutableSet alloc] init];
id stringHolder;
numberofArrayElements = [self count];
while (loop < numberofArrayElements) {
searchResults.length = 0;
searchResults = [[self objectAtIndex: loop] rangeOfString: matchSought options:NSCaseInsensitiveSearch];
if (searchResults.length > 0) {
stringHolder = [self objectAtIndex: loop];
[resultCollectorArray addObject: stringHolder];
}
loop++;
}
return [resultCollectorArray autorelease];
}
Once we get back to the main portion of the program, I get an unrecognized selector sent to the mutable array that was supposed to receive the result of the method. Here's the main section:
#import <Foundation/Foundation.h>
#import "LookupInArray.h"
int main (int argc, const char * argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
NSString *testString = [[NSString alloc] initWithString: #"ab"];
NSMutableString * resultString = [[NSString alloc] init];
NSArray * theArray = [[NSArray alloc] initWithObjects: ..., nil]; // Actual code has the objects
NSMutableArray *resultArray = [[NSMutableArray alloc] init];
NSUInteger arrayCount = 0;
unsigned long loops = 0;
resultArray = [theArray checkForString: testString];
arrayCount = [resultArray count];
while (loops < arrayCount){
resultString = [resultArray objectAtIndex: loops]; // Here's where we get the unrecognized selector.
NSLog(#"%#", resultString);
loops++;
}
[pool drain]; // Also, I'll release the objects later. I just want to get what's above working first.
return 0;
}
I've searched the other answers (for hours now), but didn't seen anything that solved the issue.
Any and all help would be really appreciated.
And thanks beforehand.
NSMutableArray * resultCollectorArray = [[NSMutableSet alloc] init]; is so incorrect. You are creating a mutable set and assigning it to a mutable array.
You are getting unrecognized selector because objectAtIndex: is not a valid selector for NSMutableSet. Make that statement,
NSMutableArray * resultCollectorArray = [[NSMutableArray alloc] init];
A Better way
NSArray * filteredArray = [array filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF contains[cd] %#", searchString]];
You can directly filter the array using predicates. This way you do this in a single step. :)