I can get the last element from an NSMutableArray with "lastObject". If the array was not initialized, it will return nil. Is there a similiar method or way to get this effect for the first object? This would be very helpful for me.
New update in ios 7
NSArray *array = #[#1, #2, #3];
NSLog(#"First Object: %#", [array firstObject]); // 1
NSLog(#"Last Object: %#", [array lastObject]); // 3
Something like this?
id myFirstObject = myArray.count>0 ? myArray[0] : nil;
If you particularly want this to be part of an array, make it a category :
#interface NSArray (firstObject)
- (id)firstObject;
#end
#implementation NSArray (firstObject)
- (id)firstObject {
return myArray.count>0 ? myArray[0] : nil;
}
#end
Then you get a firstObject that behaves the same as lastObject.
Why don't you just do
if ([array count] > 0) {
id x = [array objectAtIndex:0];
}
Related
My while loop doesn't seem to work. When loading this view, the app freezes.
When I delete the part of code, containing the while loop, the app won't freeze.
What I'm searching for is a piece of code that will cause that the same array is not chosen twice.
#interface ThirdViewController ()
#end
#implementation ThirdViewController
...
NSString * Answer = #"";
NSArray * RAMArray;
...
- (void)NewQuestion
{
NSString * PlistString = [[NSBundle mainBundle] pathForResource:#"Questions" ofType:#"plist"];
NSMutableArray * PlistArray = [[NSMutableArray alloc]initWithContentsOfFile:PlistString];
NSArray *PlistRandom = [PlistArray objectAtIndex: random()%[PlistArray count]];
while (![PlistRandom isEqual: RAMArray])
{
NSArray *PlistRandom = [PlistArray objectAtIndex: random()%[PlistArray count]];
}
RAMArray = PlistRandom;
...
}
- (void)Check:(NSString*)Choise
{
...
if ([Choise isEqualToString: Answer])
{
...
[self NewQuestion];
}
}
- (IBAction)AnsButA:(id)sender
{
UIButton *ResultButton = (UIButton *)sender;
NSString *Click = ResultButton.currentTitle;
[self Check:Click];
}
My guess is that because you re-declare PlistRandom within the while loop, the inner-declared variable may be out of scope at the point the while conditionis evaluated. Your problem I think is a scoping issue, just change the loop to this and see if that works:
while (![PlistRandom isEqual: RAMArray])
{
PlistRandom = [PlistArray objectAtIndex: random()%[PlistArray count]];
}
I feel like I have read many (simple) examples that do exactly what I am trying to do. I just cannot seem to get this to work. I need a second eye on my code, and I don't have anyone around, so pardon me if this seems very simple... The code compiles without a problem. Thank you!
#implementation Engine
- (id) initWithInventory: (NSString *) path {
if (self = [super init]) {
NSString *contents = [NSString stringWithContentsOfFile:#"ingredientList.csv" encoding:NSASCIIStringEncoding error:nil];
NSLog(#"%#",contents); // This yields the contents of the file appropriately
NSArray *lines = [contents componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
NSRange ingredientRange = {0,96}; // This is done because I want to omit the last element of the array... the 97th is an empty string caused by the end of file newline character. I know it's bad coding...
NSEnumerator *enumerator = [[lines subarrayWithRange:ingredientRange] objectEnumerator];
NSString *curString;
NSArray *ingredientElements;
NSRange activeEffectRange = {1,4}; // Element 0 will be the key, elements 1-4 are the array to be stored.
while (curString = [enumerator nextObject]) {
ingredientElements = [curString componentsSeparatedByString:#","];
Ingredient *theIngredient = [[Ingredient alloc] initWithName:[ingredientElements objectAtIndex:0] andActiveEffects:[ingredientElements subarrayWithRange:activeEffectRange]];
NSLog(#"%#",[theIngredient ingredientName]);
NSLog(#"%#",[theIngredient activeEffects]); //These both print out correctly.
NSString *theName = [theIngredient ingredientName];
[allIngredients setObject:theIngredient forKey:theName];
NSLog(#"%#",[allIngredients objectForKey:[theIngredient ingredientName]]); // ***This yields (null)***
}
}
return self;
}
EDIT: I should add, that allIngredients is an instance variable of the class being initiated, so it is defined properly as an NSMutableDictionary:
#interface Engine : NSObject {
NSMutableDictionary *allIngredients;
}
- (id) initWithInventory: (NSString *) path;
#end
Where are you creating allIngredients? You've declared it, but you haven't allocated it before you use it.
allIngredients = [[NSMutableDictionary alloc] init]
hi at all ,I've this code :
+(NSArray *)splatterUrls
{
NSString *jsonString = [ ApiMethod jsonOfStores];
NSDictionary *results =[jsonString objectFromJSONString];
NSArray *movieArray = [results objectForKey:#"Seasons"];
//int i=0;
// Search for year to match
for (NSDictionary *movie in movieArray)
{
NSNumber *idSplatterMovie = [movie objectForKey:#"Id"];
// NSLog(#" %#", idSplatterMovie );
NSArray *try = [movie objectForKey:#"Episodes"];
// NSLog(#"%#", try);
for (NSDictionary *op in try)
{
if([idSplatterMovie integerValue] == 46)
{
//i++;
NSArray *movieArrayString = [op objectForKey:#"Url"];
// NSLog(#" %#", movieArrayString);
return movieArrayString;
}
}
}
}
I want to return movieArrayString with all his objects and how many object contains in it. I think that I should use this method : + (id)arrayWithObjects:(const id *)objects count:(NSUInteger)count. It's possible? If yes, can you tell me how can use it?
Thank you so much!
by the way , i have to call splatterUrls method and implement in home.m that it is :
- (void)viewDidLoad
{
[super viewDidLoad];
NSArray *urlSplatter= [GetSplatterUrlsMovie splatterUrls];
NSLog(#" %#", urlSplatter);
}
Looks good as it is to me.
Do this to return your movies array, array will be equal to your movies array:
NSArray *array = [self splatterUrls];
Then to get the count/number of objects in your array do this, i is equal to the number of objects in the array:
int i = [array count];
What is the problem ??
You return a NSarray ... call the method count on your NSarray object!
I'm creating UILabels dynamically in a for each loop. Every loop that is run creates 1-4 UILabels.
What I want is that I put these UILabels into my NSMutableArray and being able later to easy retrieve the data.
My original thought was to put these UILabels into a NSDictionary and use [dictGroupLabels setValue:uiLabel1 forKey:#"uiLabel1"] and then [dictGroupLabels setValue:uiLabel2 forKey:#"uiLabel2"] and so on. And then put this dictionary into my NSMutableArray for each loop. Later on I could access the values like UILabel *label = [[myArray objectAtIndex:0] valueForKey:#"uiLabel1"] BUT that unfortunately doesn't work since UILabels don't conform to the NSCopying protocol.
So with this in mind how would you solve this?
this question provided more information on what you are trying to accomplish. Since you know for a fact, the possible set of labels you are trying to create in each case, I would highly recommend using mutable dictionaries instead of arrays.
To illustrate, given the following hypothetical class definition:
#interface MyClass: NSObject {
NSMutableDictionary * _labelDict;
}
#property (nonatomic, retain) NSMutableDictionary * labelDict;
- ( void )methodA;
- ( void )methodB;
- (NSMutableDictionary *) labelsForRunLoop: (NSUInteger) loopIdx;
#end
You would have the following, hypothetical, class implementation:
#implementation MyClass
#synthesize labelDict = _labelDict;
- ( id ) init {
if( ( self = [ super init ] ) ) {
[self setLabelDict: [NSMutableDictionary dictionaryWithCapacity: 8]];
}
}
- ( void ) dealloc {
[ self.labelDict release ];
[ super dealloc ];
}
- ( void ) methodA {
for(NSUInteger i = 0; i < some index; i++) {
[self.labelDict setObject: [self labelsForRunLoop: i] forKey: [NSString stringWithFormat: #"%d", i]];
}
}
- ( void ) methodB {
// Locate the label you need to work with. Example based on this crude pseudo code
NSMutableDictionary * subDict = (NSMutableDictionary *) [self.labelDict objectForKey: #"0"];
UILabel * theLabel = (UILabel * ) [subDict objectForKey: #"UILabel.Z"];
theLabel.text = #"Label 1";
}
- (NSMutableDictionary *) labelsForRunLoop: (NSUInteger) loopIdx {
NSMutableDictionary * dictionary = [NSMutableDictionary dictionaryWithCapacity: 4] ;
[dictionary setObject: create-w-label forKey: #"UILabel.W"];
[dictionary setObject: create-x-label forKey: #"UILabel.X"];
[dictionary setObject: create-y-label forKey: #"UILabel.Y"];
[dictionary setObject: create-z-label forKey: #"UILabel.Z"];
return [dictionary retain];
}
#end
This is basically pseudo code and will not successfully compile. However it will serve as a good starting point. You probably want to store each label dictionary under some key that makes sense, instead of just using the loop's index. Hope this helps.
They don’t need to adhere to NSCopying to be added to an array. It sounds like you just need to do something like this:
NSMutableArray *mainArray = [NSMutableArray array];
for(int i = 0; i < 5; i++)
{
NSMutableArray *subArray = [[NSMutableArray alloc] initWithCapacity:5];
for(int j = 0; j < 4; j++)
{
UILabel *label = [[UILabel alloc] init];
// etc.
[subArray addObject:label];
[label release];
}
[mainArray addObject:subArray];
[subArray release];
}
// then, to get one of the labels:
UILabel *someSpecificLabel = [[mainArray objectAtIndex:2] objectAtIndex:1];
I am trying to create a deep-copy of a NSMutableDictionary and assign it to another NSMutableDictionary. The dictionary contains a bunch of arrays, each array containing names, and the key is an alphabet (the first letter of those names). So one entry in the dictionary is 'A' -> 'Adam', 'Apple'. Here's what I saw in a book, but I'm not sure if it works:
- (NSMutableDictionary *) mutableDeepCopy
{
NSMutableDictionary * ret = [[NSMutableDictionary alloc] initWithCapacity: [self count]];
NSArray *keys = [self allKeys];
for (id key in keys)
{
id oneValue = [self valueForKey:key]; // should return the array
id oneCopy = nil;
if ([oneValue respondsToSelector: #selector(mutableDeepCopy)])
{
oneCopy = [oneValue mutableDeepCopy];
}
if ([oneValue respondsToSelector:#selector(mutableCopy)])
{
oneCopy = [oneValue mutableCopy];
}
if (oneCopy == nil) // not sure if this is needed
{
oneCopy = [oneValue copy];
}
[ret setValue:oneCopy forKey:key];
//[oneCopy release];
}
return ret;
}
should the [onecopy release] be there or not?
Here's how I'm going to call this method:
self.namesForAlphabets = [self.allNames mutableDeepCopy];
Will that be ok? Or will it cause a leak? (assume that I declare self.namesForAlphabets as a property, and release it in dealloc).
Because of toll-free bridging, you can also use the CoreFoundation function CFPropertyListCreateDeepCopy:
NSMutableDictionary *mutableCopy = (NSMutableDictionary *)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFDictionaryRef)originalDictionary, kCFPropertyListMutableContainers);
Assuming all elements of the array implement the NSCoding protocol, you can do deep copies via archiving because archiving will preserve the mutability of objects.
Something like this:
id DeepCopyViaArchiving(id<NSCoding> anObject)
{
NSData* archivedData = [NSKeyedArchiver archivedDataWithRootObject:anObject];
return [[NSKeyedUnarchiver unarchiveObjectWithData:archivedData] retain];
}
This isn't particularly efficient, though.
IMPORTANT: The question (and my code below) both deal with a very specific case, in which the NSMutableDictionary contains only arrays of strings. These solutions will not work for more complex examples. For more general case solutions, see the following:
Tom Dalling's answer
dreamlax's answer
Source from yfujiki on GitHub Gist
Answer for this specific case:
Your code should work, but you will definitely need the [oneCopy release]. The new dictionary will retain the copied objects when you add them with setValue:forKey, so if you do not call [oneCopy release], all of those objects will be retained twice.
A good rule of thumb: if you alloc, retain or copy something, you must also release it.
Note: here is some sample code that would work for certain cases only. This works because your NSMutableDictionary contains only arrays of strings (no further deep copying required):
- (NSMutableDictionary *)mutableDeepCopy
{
NSMutableDictionary * ret = [[NSMutableDictionary alloc]
initWithCapacity:[self count]];
NSMutableArray * array;
for (id key in [self allKeys])
{
array = [(NSArray *)[self objectForKey:key] mutableCopy];
[ret setValue:array forKey:key];
[array release];
}
return ret;
}
Another technique that I have seen (which is not at all very efficient) is to use an NSPropertyListSerialization object to serialise your dictionary, then you de-serialise it but specify that you want mutable leaves and containers.
NSString *errorString = nil;
NSData *binData =
[NSPropertyListSerialization dataFromPropertyList:self.allNames
format:NSPropertyListBinaryFormat_v1_0
errorString:&errorString];
if (errorString) {
// Something bad happened
[errorString release];
}
self.namesForAlphabets =
[NSPropertyListSerialization propertyListFromData:binData
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:NULL
errorDescription:&errorString];
if (errorString) {
// something bad happened
[errorString release];
}
Again, this is not at all efficient.
Trying to figure out by checking respondToSelector(#selector(mutableCopy)) won't give the desired results as all NSObject-based objects respond to this selector (it's part of NSObject). Instead we have to query if an object conforms to NSMutableCopying or at least NSCopying. Here's my answer based on this gist mentioned in the accepted answer:
For NSDictionary:
#implementation NSDictionary (MutableDeepCopy)
// As seen here (in the comments): https://gist.github.com/yfujiki/1664847
- (NSMutableDictionary *)mutableDeepCopy
{
NSMutableDictionary *returnDict = [[NSMutableDictionary alloc] initWithCapacity:self.count];
NSArray *keys = [self allKeys];
for(id key in keys) {
id oneValue = [self objectForKey:key];
id oneCopy = nil;
if([oneValue respondsToSelector:#selector(mutableDeepCopy)]) {
oneCopy = [oneValue mutableDeepCopy];
} else if([oneValue conformsToProtocol:#protocol(NSMutableCopying)]) {
oneCopy = [oneValue mutableCopy];
} else if([oneValue conformsToProtocol:#protocol(NSCopying)]){
oneCopy = [oneValue copy];
} else {
oneCopy = oneValue;
}
[returnDict setValue:oneCopy forKey:key];
}
return returnDict;
}
#end
For NSArray:
#implementation NSArray (MutableDeepCopy)
- (NSMutableArray *)mutableDeepCopy
{
NSMutableArray *returnArray = [[NSMutableArray alloc] initWithCapacity:self.count];
for(id oneValue in self) {
id oneCopy = nil;
if([oneValue respondsToSelector:#selector(mutableDeepCopy)]) {
oneCopy = [oneValue mutableDeepCopy];
} else if([oneValue conformsToProtocol:#protocol(NSMutableCopying)]) {
oneCopy = [oneValue mutableCopy];
} else if([oneValue conformsToProtocol:#protocol(NSCopying)]){
oneCopy = [oneValue copy];
} else {
oneCopy = oneValue;
}
[returnArray addObject:oneCopy];
}
return returnArray;
}
#end
Both methods have the same internal to-copy-or-not-to-copy logic and that could be extracted into a separate method but I left it like this for clarity.
For ARC - note kCFPropertyListMutableContainersAndLeaves for truly deep mutability.
NSMutableDictionary* mutableDict = (NSMutableDictionary *)
CFBridgingRelease(
CFPropertyListCreateDeepCopy(kCFAllocatorDefault,
(CFDictionaryRef)someNSDict,
kCFPropertyListMutableContainersAndLeaves));
Thought I'd update with an answer if you're using ARC.
The solution Weva has provided works just fine. Nowadays you could do it like this:
NSMutableDictionary *mutableCopy = (NSMutableDictionary *)CFBridgingRelease(CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFDictionaryRef)originalDict, kCFPropertyListMutableContainers));
Useful answers here, but CFPropertyListCreateDeepCopy doesn't handle [NSNull null] in the data, which is pretty normal with JSON decoded data, for example.
I'm using this category:
#import <Foundation/Foundation.h>
#interface NSObject (ATMutableDeepCopy)
- (id)mutableDeepCopy;
#end
Implementation (feel free to alter / extend):
#implementation NSObject (ATMutableDeepCopy)
- (id)mutableDeepCopy
{
return [self copy];
}
#end
#pragma mark - NSDictionary
#implementation NSDictionary (ATMutableDeepCopy)
- (id)mutableDeepCopy
{
return [NSMutableDictionary dictionaryWithObjects:self.allValues.mutableDeepCopy
forKeys:self.allKeys.mutableDeepCopy];
}
#end
#pragma mark - NSArray
#implementation NSArray (ATMutableDeepCopy)
- (id)mutableDeepCopy
{
NSMutableArray *const mutableDeepCopy = [NSMutableArray new];
for (id object in self) {
[mutableDeepCopy addObject:[object mutableDeepCopy]];
}
return mutableDeepCopy;
}
#end
#pragma mark - NSNull
#implementation NSNull (ATMutableDeepCopy)
- (id)mutableDeepCopy
{
return self;
}
#end
Example extensions – strings are left as normal copies. You could override this if you want to be able to in place edit them. I only needed to monkey with a deep down dictionary for some testing, so I've not implemented that.