I have done a bit of searching and not really found an answer to my question.
The code below is trying to copy the contents of a NSMutable array that contains some objects.
I have tried the code below however when run there is no error, but the new arrays do not get the objects as I would have thought they would.
csvContent is a array that contains objects from parsing a CSV file and the other NSMutable arrays round1, round2 etc have been defined in the header file.
The NSLOG output is correct but the arrays contain no objects.
for(int loopNumber = 0; loopNumber < [csvContent count]; loopNumber++)
{
if ([[[csvContent objectAtIndex:loopNumber] objectAtIndex:1] isEqualToString:#"1"])
{
[round1 addObject:[csvContent objectAtIndex:loopNumber]];
NSLog(#"round 1");
}
if ([[[csvContent objectAtIndex:loopNumber] objectAtIndex:1] isEqualToString:#"2"])
{
[round2 addObject:[csvContent objectAtIndex:loopNumber]];
NSLog(#"round 2");
}
if ([[[csvContent objectAtIndex:loopNumber] objectAtIndex:1] isEqualToString:#"3"])
{
[round3 addObject:[csvContent objectAtIndex:loopNumber]];
NSLog(#"round 3");
}
}
Did you actually create and initialize the arrays for round1, round2, and round3? In other words, make sure they are not nil when this loop is run.
Also, your code is terribly inefficient. You call [csvContent objectAtIndex:loopNumber] six times inside the loop. Try this (I'm using i instead of loopNumber to save typing):
for (int i = 0; i < csvContent.count; i++) {
NSArray *loopContent = csvContent[i];
NSString *val = loopContent[1];
if ([val isEqualToString:#"1"]) {
[round1 addObject:loopObject];
} else if ([val isEqualToString:#"2"]) {
[round2 addObject:loopObject];
} else if ([val isEqualToString:#"3"]) {
[round3 addObject:loopObject];
}
}
Related
I am using a nsmutablearray in loop and want to remove its object (or assign nil) that has just traversed.
But if I am doing so, I get an error as <__NSArrayM: 0x8c3d3a0> was mutated while being enumerated.' . The code is as below
- (TreeNode*)depthLimitedSearch:(TreeNode *)current costLimit:(int)currentCostBound {
NSMutableArray *children=[NSMutableArray arrayWithArray:[current expandNodeToChildren]];
for (TreeNode *s in children) {
if (s.puzzleBox.isFinalPuzzleBox) {//checking for final puzzleBox
return s;
}
/*exploredNodes++;
if (exploredNodes %10000==0) {
NSLog(#"explored nodes for this treshold-%d are %d",currentCostBound,exploredNodes);
}*/
int currentCost =[s.cost intValue]+[s.heuristicsCost intValue];
if (currentCost <= currentCostBound) {
//[s.puzzleBox displayPuzzleBox];
TreeNode *solution = [self depthLimitedSearch:s costLimit:currentCostBound];
if (solution!=nil){//&& (bestSolution ==nil|| [solution.cost intValue] < [bestSolution.cost intValue])) {
bestSolution = solution;
return bestSolution;
}
}else {
if (currentCost < newLimit) {
//NSLog(#"new limit %d", currentCost);
newLimit = currentCost;
}
}
// here I want to free memory used by current child in children
[children removeObject:s]
}
children=nil;
return nil;
}
and I have commented the place where I want to release the space used by the child.
You should not be using a for...in loop if you want to remove elements in the array. Instead, you should use a normal for loop and go backwards in order to make sure you don't skip any items.
for (NSInteger i = items.count - 1; i >= 0; i--) {
if (someCondition) {
[items removeObjectAtIndex:i];
}
}
You can collect the items to be removed in another array and remove them in a single pass afterwards:
NSMutableArray *toRemove = [NSMutableArray array];
for (id candidate in items) {
if (something) {
[toRemove addObject:candidate];
}
}
[items removeObjectsInArray:toRemove];
It’s easier than iterating over indexes by hand, which just asking for off-by-one errors.
Not sure how this plays with your early returns, though.
In my app I'me getting responses from the server and I have to check that I don't create duplicate objects in the NSArray which contains NSDictionaries. Now to check if the objects exists I do this:
for (int i = 0; i < appDelegate.currentUser.userSiteDetailsArray.count; i++){
NSDictionary *tmpDictionary = [appDelegate.currentUser.userSiteDetailsArray objectAtIndex:i];
if ([[tmpDictionary valueForKey:#"webpropID"] isEqualToString:tmpWebproperty.identifier]){
needToCheck = NO;
}
if (i == appDelegate.currentUser.userSiteDetailsArray.count - 1 && ![[tmpDictionary valueForKey:#"webpropID"] isEqualToString:tmpWebproperty.identifier] && needToCheck){
// It means it's the last object we've iterated through and needToCheck is still = YES;
//Doing stuff here
}
}
I set up a BOOL value because this iteration goes numerous times inside a method and I can't use return to stop it. I think there is a better way to perform this check and I would like to hear your suggestions about it.
BOOL needToCheck = YES;
for (int i = 0; i < appDelegate.currentUser.userSiteDetailsArray.count; i++){
NSDictionary *tmpDictionary = [appDelegate.currentUser.userSiteDetailsArray objectAtIndex:i];
if ([[tmpDictionary valueForKey:#"webpropID"] isEqualToString:tmpWebproperty.identifier]){
needToCheck = NO;
break;
}
}
if (needToCheck) {
//Doing stuff here
}
But, as others have said, you can maybe keep a "summary" in a separate NSSet that you check first, vs spinning through all the dictionaries.
NSDictionary *previousThing = nil;
for (NSDictionary *thing in appDelegate.currentUser.userSiteDetailsArray) {
if ([thing[#"webpropID"] isEqualToString:newWebPropertyIdentifier]) {
previousThing = thing;
break;
}
}
if (previousThing == nil) {
// no previous thing
} else {
// duplicate
}
How do I refactor similar methods for the following (Objective C)?
- (void)insertNewSong:(Song *)newSong forArtist:(Artist *)artist {
NSMutableArray *newSongList = [[artist songs] mutableCopy];
BOOL hasInserted = NO;
for (int i = 0; i < [[artist songs] count]; i++) {
Song *existingSong = [[artist songs] objectAtIndex:i];
if ([[newSong title] caseInsensitiveCompare:[existingSong title]] == NSOrderedAscending) {
[newSongList insertObject:newSong atIndex:i];
hasInserted = YES;
break;
}
}
if (hasInserted == NO) {
[newSongList addObject:newSong];
}
artist.songs = newSongList;
}
- (void)insertNewArtistToSongList:(Artist *)newArtist {
BOOL hasInserted = NO;
for (int i = 0; i < [_artists count]; i++) {
Artist *existingArtist = [_artists objectAtIndex:i];
if ([[newArtist name] caseInsensitiveCompare:[existingArtist name]] == NSOrderedAscending) {
[_artists insertObject:newArtist atIndex:i];
hasInserted = YES;
break;
}
}
if (hasInserted == NO) {
[_artists addObject:newArtist];
}
}
For the insertNewSong method, a NSMutableArray [artist songs] containing each Song object is used.
For the insertNewArtist method, a NSMutableArray instance variable _artists containing each Artist Object is used.
Both methods insert an object into an NSMutableArray by comparing the text property of the input object against the text property found within the arrays.
Currently the above methods contain some duplication but is easy to understand (in my case). I was thinking whether there might be a way of simplifying it into a more general method, and does not hurt readability?
There is no general rule, but here are some general rules:
Sometimes it makes sense to combine code like this, sometimes not. Lots of pluses/minuses.
Sometimes it's best to abstract PART of the operation, and leave the other part custom.
Generally, if you have a lot of "if thingA then do this, else that" logic, you've done it wrong (or should not do it at all).
It's best when you can write a single routine and just pass in different parameters (that aren't simply Boolean switches) to differentiate the multiple cases.
It's hard.
And, as a general rule, I don't try too hard to abstract until I have the third instance of nearly the same logic.
(Generally speaking.)
I have array made from JSON response.
NSLog(#"%#", arrayFromString) gives the following:
{
meta = {
code = 200;
};
response = {
groups = (
{
items = (
{
categories = (
{
icon =
"http://foursquare.com/img/categories/parks_outdoors/default.png";
id = 4bf58dd8d48988d163941735;
and so on...
This code
NSArray *arr = [NSArray arrayWithObject:[arrayFromString valueForKeyPath:#"response.groups.items"]];
gives array with just one element that I cannot iterate through. But if I write it out using NSLog I can see all elements of it.
At the end I would like to have an array of items that I can iterate through to build a datasource for table view for my iPhone app.
How would I accomplish this?
EDIT:
I have resolved my issue by getting values from the nested array (objectAtIndex:0):
for(NSDictionary *ar in [[arrayFromString valueForKeyPath:#"response.groups.items"] objectAtIndex:0]) {
NSLog(#"Array: %#", [ar objectForKey:#"name"]);
}
First, the data structure you get back from the JSON parser is not an array but a dictionary: { key = value; ... } (curly braces).
Second, if you want to access a nested structure like the items, you need to use NSObject's valueForKeyPath: method. This will return an array of all items in your data structure:
NSLog(#"items: %#", [arrayFromString valueForKeyPath:#"response.groups.items"]);
Note that you will loose the notion of groups when retrieving the item objects like this.
Looking at the JSON string you posted, response.groups.items looks to be an array containing one item, a map/dictionary containing one key, "categories." Logging it out to a string is going to traverse the whole tree, but to access it programmatically, you have to walk the tree yourself. Without seeing a more complete example of the JSON, it's hard to say exactly what the right thing to do is here.
EDIT:
Traversing an object graph like this is not that simple; there are multiple different approaches (depth-first, breadth-first, etc,) so it's not necessarily something for which there's going to be a simple API for you to use. I'm not sure if this is the same JSON library that you're using, but, for instance, this is the code from a JSON library that does the work of generating the string that you're seeing. As you can see, it's a bit involved -- certainly not a one-liner or anything.
You could try this, which I present without testing or warranty:
void __Traverse(id object, NSUInteger depth)
{
NSMutableString* indent = [NSMutableString string];
for (NSUInteger i = 0; i < depth; i++) [indent appendString: #"\t"];
id nextObject = nil;
if ([object isKindOfClass: [NSDictionary class]])
{
NSLog(#"%#Dictionary {", indent);
NSEnumerator* keys = [(NSDictionary*)object keyEnumerator];
while (nextObject = [keys nextObject])
{
NSLog(#"%#\tKey: %# Value: ", indent, nextObject);
__Traverse([(NSDictionary*)object objectForKey: nextObject], depth+1);
}
NSLog(#"%#}", indent);
}
else if ([object isKindOfClass: [NSArray class]])
{
NSEnumerator* objects = [(NSArray*)object objectEnumerator];
NSLog(#"%#Array (", indent);
while (nextObject = [objects nextObject])
{
__Traverse(nextObject, depth+1);
}
NSLog(#"%#)", indent);
}
else
{
NSLog(#"%#%#",indent, object);
}
}
void Traverse(id object)
{
__Traverse(object, 0);
}
I need to pick string valur from an NSMutableArray then save it into a plist. I've builded an NSMutableArray to display infos in table View. Maximum allowed index is 8. (paste just two in example)
The problem if the String doesn't exist, I get the following error:
sDict is a dictionary for saving datas to a property list file.
the code:
- (IBAction)save:(id)sender {
(...)
NSString *One;
NSString *Two;
...etc
if ([self.smOne objectAtIndex:0])
One = [self.smOne objectAtIndex:0];
if ([self.smOne objectAtIndex:1])
Two = [self.smOne objectAtIndex:1];
...etc
if (One)
[sDict setObject:[self.smTwo objectAtIndex:0]
forKey:[UserM stringByAppendingString:One]];
[sDict setObject:[self.smThree objectAtIndex:0]
forKey:[UserS stringByAppendingString:One]];
[sDict setObject:[self.smFour objectAtIndex:0]
forKey:[UserP stringByAppendingString:One]];
if (Two)
[sDict setObject:[self.smTwo objectAtIndex:1]
forKey:[UserM stringByAppendingString:Two]];
[sDict setObject:[self.smThree objectAtIndex:1]
forKey:[UserS stringByAppendingString:Two]];
[sDict setObject:[self.smFour objectAtIndex:1]
forKey:[UserParM stringByAppendingString:Two]];
...etc
}
This code works if all objects are present, but fails if it miss one of the object at index.
I really don't know how to check properly if the object is present or not, cause code above seem's to don't works well.
I've tried with [self.smOne count] but as problem to pass as a Int or String to make conditions with.
Thanks for answer.
it looks like you're explicitly checking smOne from indices 1 through 8. But you also mentioned that the array can have up to 8. So if it's missing, say, 6, 7 and 8, you'd still be calling [smOne objectAtIndex:6], which would result in an NSRangeException being raised as 6 is out of bounds for the array.
try this instead:
int i = 0;
for ( NSString *aString in self.smOne )
{
[sDict setObject:[self.smTwo objectAtIndex:i]
forKey:[UserM stringByAppendingSting:aString]];
[sDict setObject:[self.smThree objectAtIndex:i]
forKey:[UserS stringByAppendingString:aString]];
[sDict setObject:[self.smFour objectAtIndex:i]
forKey:[UserP stringByAppendingString:aString]];
i++;
}
it'll go through each object in the smOne array and add the object into sDict regardless of how many items you have in smOne.
also, be careful with how you're generating your keys. there's the possibility that [UserM stringByAppendingSting:aString] won't always be unique.
Sorry to ask again but i have dificulties to find how to rebuild arrays from the key/string couple saved with the loop.
i've tried this:
int i = 0;
for (NSString *SMServ in [temp objectForKey:
[UserMen stringByAppendingFormat:#"%d",i]]){
NSString *SMMem[i];
SMMem[i] = [temp objectForKey:[UserMen stringByAppendingFormat:#"%d",i]];
NSArray *theArray = [ NSArray arrayWithObjects:SMMem count:i];
i++;
}
But nothing happens.
if i try with for (i = 0; i < 9; i ++) and (i + 1) instead of [i], i get same bounds errors in the first example.
thanks again for help.
Well, finally it ,works. Thanks for link to the documentation, i read too fast last time.
I'm sure this is not the cleanest way, but it works with this loop:
for (key in sDict) {
if ([sDict valueForKey:[UserMen stringByAppendingFormat:#"%d",i]]) {
tempMe = [sDict valueForKey:[UserMen stringByAppendingFormat:#"%d",i]];
if (tempMe) {
[manArray insertObject:tempMe atIndex:(0 + a)];
[bankArray insertObject:[NSString stringWithFormat:#"%d",i] atIndex:(0 + a)];
a++;
}
}
if ([sDict valueForKey:[UserSerial stringByAppendingFormat:#"%d",i]]) {
SMSer = [sDict valueForKey:[UserSerial stringByAppendingFormat:#"%d",i]];
if (SMSer) {
[serArray insertObject:SMSer atIndex:(0 + b)];
b++;
}
}
if ([sDict valueForKey:[UserPart stringByAppendingFormat:#"%d",i]]) {
SMPart = [sDict valueForKey:[UserPart stringByAppendingFormat:#"%d",i]];
if (SMPart) {
[partArray insertObject:SMPart atIndex:(0 + c)];
c++;
}
}
i++;
}