I'm making a code which shows the names of people on a list.
The list is different for each date, so my problem is when there is only like 1 or no people signed and I make an array with index beyond the limit of people, it crashed. I know that this happens because the array is empty, but how do I make the code ignore empty arrays?
I have tried to make an "if" that count the number of arrays and then decide to post the array or just post no name. But it doesn't work like this, I still get the out of bounds exception.
How should I manage empty arrays?
My code:
NSString *html = [request2 responseString];
NSMutableArray *arr2 = [html componentsSeparatedByString:#"vagter"];
NSString *html1 = [arr2 objectAtIndex:1];
//name1
NSMutableArray *arr3 = [html1 componentsSeparatedByString:#"<td><font color=#ffffff>"];
NSString *html2 = [arr3 objectAtIndex:1];
NSMutableArray *arr4 = [html2 componentsSeparatedByString:#"</font></td>"];
NSString *html3 = [arr4 objectAtIndex:0];
_name.text = html3;
//name 2
NSMutableArray *arr5 = [html1 componentsSeparatedByString:#"<td><font color=#ffffff>"];
if ([arr5 count] > 4) {
NSString *html4 = [arr5 objectAtIndex:5];
NSMutableArray *arr6 = [html4 componentsSeparatedByString:#"</font></td>"];
NSString *html5 = [arr6 objectAtIndex:0];
_name.text = html5;
}
else
{
_name1.text = #"No name";
}
It should be:
if ([arr5 count] > 5) {
NSString *html4 = [arr5 objectAtIndex:5];
...
Indeed, index 5 will correspond to the sixth array item, so you have to have at least 6 objects in it.
Use the same pattern, if you want to check for the array bounds, in all cases.
The problem is that you expect the return from componentsSeparatedByString to return consistent results according to your expectations.
Clearly thats not working.
Array handling is simple. Dont ask for objects that arent there.
Check the count and only access indexes from 0 to count - 1;
If count is zero dont access anything.
Related
THIS IS WHERE THE PROBLEM LIES
NSString *individualEventTitle;
NSMutableArray *eventTitleArray = [[NSMutableArray alloc]init];
for (NSUInteger index =0; (index < 8) ; index++){
EventsList *eventList = [[EventsList alloc] initWithIndex:index];
NSString *individualEventTitle = eventList.eventTitle;
/*self.eventTitleArray = eventList.eventTitle;
self.eventLocationArray = eventList.eventLocation;
self.eventIconArray = eventList.eventIcon;
self.eventPriceArray = eventList.eventPrice;
self.eventTypeArray = eventList.eventType;*/
[eventTitleArray addObject:individualEventTitle];
NSLog(#"Title of Event:%#", individualEventTitle);
NSLog(#"Array of Event:%#", eventTitleArray);
}
So from my understanding, the loop should go through itself 8 times (to account for the number of items in my class array). To confirm this I NSLogged a string for the eventList.eventTitle and assigned it to a string called individualEventTitle. Upon reading the console I received ALL 8 event Titles.
However, when I add the command at the end of the loop, to add that string to the NSMutableArray *eventTitleArray. It appears null in the console when NSlogged.
I would highly appreciate some help, as I've spend the last two nights just tinkering with it with no avail!
Thank you!
Contents of my console
Console
Try to replace this line
[eventTitleArray addObject:[NSString stringWithFormat:#"%#",individualEventTitle]];
I have this snipped of code that results in an array with a whole bunch of "<null>" throughout and I need to figure out how to remove them. Obviously after smashing my head against the keyboard I'm asking for some help.
In my .h I have declared:
NSArray *sortedContacts;
NSArray *rawContacts;
And then in .m:
-(void) buildContacts {
ABAddressBook *addressBook = [ABAddressBook sharedAddressBook];
NSArray *contacts = [addressBook people];
rawContacts=contacts;
NSArray *firstNames = [rawContacts valueForKey:#"First"];
NSArray *lastNames = [rawContacts valueForKey:#"Last"];
NSArray *organization = [rawContacts valueForKey:#"Organization"];
NSMutableArray *fullNames = [NSMutableArray array];
for(int i = 0; i < [firstNames count]; i++)
{
NSString *fullName = [NSString stringWithFormat:#"%# %# %#",
[firstNames objectAtIndex:i],
[lastNames objectAtIndex:i],
[organization objectAtIndex:i]];
[fullNames addObject:fullName];
}
NSMutableArray *fullList = [[NSMutableArray alloc]initWithArray:fullNames];
[fullList removeObjectIdenticalTo: #"<null>"];
sortedContacts = [fullList sortedArrayUsingSelector:#selector(compare:)];
NSLog(#"%#",sortedContacts);
}
I've tried so many things that I just can't see the forest for the trees anymore.
The text <null> is how the singleton instance of NSNull describes itself. That is, it's what -[NSNull description] returns.
In turn, these NSNull objects are getting into your firstNames, lastNames, and organization arrays because that's what Key-Value Coding does when you call -valueForKey: on an array and some of the elements return nil when that message is forwarded on to them with the same key. That is, calling [rawContacts valueForKey:#"First"] causes NSArray to call [element valueForKey:#"First"] for each element in rawContacts and to put the result in the array it builds. But, since an array can't contain nil, if one of those elements returns nil from [element valueForKey:#"First"], an NSNull object is added in its place.
Then, you are formatting the string fullName from the corresponding elements of firstNames, lastNames, and organization. You need to check if any of those elements are NSNull using if ([value isKindOfClass:[NSNull class]]) and handling that. For instance, you might just skip that record. Or you might combine the available fields and leave out any unavailable ones.
In any case, none of the elements of fullList will be #"<null>" because formatting values into #"%# %# %#" can never result in that string. (It might be #"<null> <null> <null>" or something like that, but never just #"<null>".)
A quick look at your code suggests you cannot get any empty strings added to your array, (a) you add elements using:
[fullNames addObject:fullName];
and fullName is created using:
[NSString stringWithFormat:#"%# %# %#" ...
so even if the %#'s get replaced by nothing you'll still have 2 spaces...
Maybe this is why all the things you've tried fail, if you're looking for empty strings you won't find them.
(Addendum: Question now says you're looking for #"<null>", you won't get that either for the same reason - there is at least two spaces in your string.)
The simple answer to removing invalid entries in fullNames is not to add them in the first place. You are adding elements in a loop (for), and conditional logic (e.g. if) inside the loop to determine whether you have something valid to add - however you define "something valid" - and only add an item to fullNames if so.
HTH
I'm not really familiar with the AddressBook framework, however this might be what's causing the confusion:
The values you collect in your arrays firstNames, lastNames and organization can be of type NSString or NSNull. You have to do any null-checking within the for-loop, before the fullName-string is constructed.
Remove this useless line:
[fullList removeObjectIdenticalTo: #"<null>"];
And replace the contents of your for-loop with the following code:
for(int i = 0; i < [firstNames count]; i++)
{
NSString *firstName = [firstNames objectAtIndex:i];
NSString *lastName = [lastNames objectAtIndex:i];
NSString *org = [organization objectAtIndex:i];
NSMutableArray *namesArray = [NSMutableArray array];
if ([firstName isKindOfClass:[NSString class]])
[namesArray addObject:firstName];
if ([lastName isKindOfClass:[NSString class]])
[namesArray addObject:lastName];
if ([org isKindOfClass:[NSString class]])
[namesArray addObject:org];
if (namesArray.count > 0)
[fullNames addObject:[namesArray componentsJoinedByString:#" "]];
}
I get an array from a JSON and I parse it into an NSMutableArray (this part is correct and working). I now want to take that array and print the first object to a Label. Here is my code:
NSDictionary *title = [[dictionary objectForKey:#"title"] objectAtIndex:2];
arrayLabel = [title objectForKey:#"label"];
NSLog(#"arrayLabel = %#", arrayLabel); // Returns correct
//Here is where I need help
string = [arrayLabel objectAtIndex:1]; //I do not get the first label (App crashes)
NSLog(#"string = %#", string);
other things that I have already tried are as follows:
string = [NSString stringWithFormat:#"%#", [arrayImage objectAtIndex:1]];
and
string = [[NSString alloc] initWithFormat:#"%#", [arrayImage objectAtIndex:1]];
Any help is greatly appriciated!
EDIT: The app does not return a single value and crashes.
Your code doesn't match the structure of your JSON. In your comment on the deleted answer, you said you got an exception when sending objectAtIndex: to an NSString. In your case, arrayLabel isn't an array when you think it is.
If your JSON has an object, your code needs to treat it as an NSDictionary. Likewise for arrays and NSArray and strings and NSString.
In addition to whatever else was going on, you repeatedly refer to "first" but use the index 1. In most C-based programming languages (and others, as well) the convention is that indexes into arrays are 0-based. So, use index 0 to get the first element.
I am using this code in a loop to populate an NSMutable Array of NSMutableSets (of NSString objects). The index of the NSSet is based on the length of the word.
// if set of this length not initialized yet, initialize set.
wordIndex = [NSString stringWithFormat:#"%d", currentWordLength];
if ([myWordArray objectForKey:wordIndex] == nil)
[myWordArray setObject:[[NSMutableSet alloc] initWithObjects:currentWord, nil] forKey:wordIndex];
else
[[myWordArray objectForKey:wordIndex] addObject:currentWord];
The final intention is to split up an array of words into an array of sets of words grouped by their lengths.
However, I see that [myWordArray count] is 0 after this. Why?
You are confusing the methods of NSMutableDictionary and NSMutableArray: In Objective-C arrays do not have keys but have indexes. If you change the class for myWordArray to NSMutableDicitionary it should work.
Try this, it looks very much like your logic, but (1) it uses NSNumbers as keys, which makes a little more sense, (2) handles the missing set condition more simply, but just adding the set, and (3) breaks up the source lines somewhat for easier debugging...
NSArray *inputStrings = // however these are initialized goes here
NSMutableDictionary *result = [NSMutableDictionary dictionary];
for (NSString *currentString in inputStrings) {
NSInteger currentWordLength = currentString.length;
wordIndex = [NSNumber numberWithInt:currentWordLength];
NSMutableSet *wordSet = [result objectForKey:wordIndex];
if (!wordSet) {
wordSet = [NSMutableSet set];
[result setObject:wordSet forKey:wordIndex];
}
[wordSet addObject:currentWord];
}
If you still have an empty dictionary after running this, it might be simpler to watch what's happening by stepping through it.
So I have an NSDictionary where the keys are years as NSString's and the value for each key is also an NSString which is sort of a description for the year. So for example, one key is "943 B.C.", another "1886". The problem I am encountering is that I want to sort them, naturally, in ascending order.
The thing is that the data source of these years is already in order, it's just that when I go ahead and call setValue:forKey the order is lost, naturally. I imagine figuring out a way to sort these NSString's might be a pain and instead I should look for a method of preserving the order at the insertion phase. What should I do? Should I instead make this an NSMutableArray in which every object is actually an NSDictionary consisting of the key being the year and the value being the description?
I guess I just answered my own question, but to avoid having wasted this time I'll leave this up in case anyone can recommend a better way of doing this.
Thanks!
EDIT: I went ahead with my own idea of NSMutableArray with NSDictionary entries to hold the key/value pairs. This is how I am accessing the information later on, hopefully I'm doing this correctly:
// parsedData is the NSMutableArray which holdes the NSDictionary entries
for (id entry in parsedData) {
NSString *year = [[entry allKeys] objectAtIndex:0];
NSString *text = [entry objectForKey:year];
NSLog(#"Year: %#, Text: %#", year, text);
}
Maintain a NSMutableArray to store the keys in order, in addition to the NSDictionary which holds all key-value pairs.
Here is a similar question.
You could either do it as an array of dictionaries, as you suggest, or as an array of strings where the strings are the keys to your original dictionary. The latter is probably a simpler way of going about it. NSDictionary does not, as I understand it, maintain any particular ordering of its keys, so attempting to sort the values there may be unwise.
I needed to solve a similar problem to sort strings of operating system names, such as "Ubuntu 10.04 (lucid)".
In my case, the string could have any value, so I sort by tokenizing and testing to see if a token is a number. I'm also accounting for a string like "8.04.2" being considered a number, so I have a nested level of tokenizing. Luckily, the nested loop is typically only one iteration.
This is from the upcoming OpenStack iPhone app.
- (NSComparisonResult)compare:(ComputeModel *)aComputeModel {
NSComparisonResult result = NSOrderedSame;
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
NSArray *tokensA = [self.name componentsSeparatedByString:#" "];
NSArray *tokensB = [aComputeModel.name componentsSeparatedByString:#" "];
for (int i = 0; (i < [tokensA count] || i < [tokensB count]) && result == NSOrderedSame; i++) {
NSString *tokenA = [tokensA objectAtIndex:i];
NSString *tokenB = [tokensB objectAtIndex:i];
// problem: 8.04.2 is not a number, so we need to tokenize again on .
NSArray *versionTokensA = [tokenA componentsSeparatedByString:#"."];
NSArray *versionTokensB = [tokenB componentsSeparatedByString:#"."];
for (int j = 0; (j < [versionTokensA count] || j < [versionTokensB count]) && result == NSOrderedSame; j++) {
NSString *versionTokenA = [versionTokensA objectAtIndex:j];
NSString *versionTokenB = [versionTokensB objectAtIndex:j];
NSNumber *numberA = [formatter numberFromString:versionTokenA];
NSNumber *numberB = [formatter numberFromString:versionTokenB];
if (numberA && numberB) {
result = [numberA compare:numberB];
} else {
result = [versionTokenA compare:versionTokenB];
}
}
}
[formatter release];
return result;
}