String conversion for elements in NSMutableArray - iphone

So I have one NSArray that has names of documents to be presented in a UITableView. The NSStrings in the NSArray have spaces so an entry would look like, "John Smith". Then I have pdfs that correspond to each of the table entries. These pdf entries are not the same name. They would be something like, "JohnSmith.pdf". I created a method to basically convert the names to the pdfs in order to present the appropriate pdfs. In my method, I basically hard coded the values
NSUInteger loopCount = 0;
for ( ; loopCount < [array count]; loopCount++) {
if ([[array objectAtIndex:loopCount] isEqualToString:#"John Smith"]) {
[array replaceObjectAtIndex:loopCount withObject:#"JohnSmith.pdf"];
}
}
Is there a better way to do this? That's all I could think of since the data was already made to have different names. Thx.


maybe you can use something like this:
NSString *filename = [[name stringByReplacingOccurrencesOfString:#" " withString:#""] stringByAppendingPathExtension:#"pdf"];


NSUInteger loopCount = 0;
for ( ; loopCount < [array count]; loopCount++) {
NSString* name = [array objectAtIndex:loopCount];
[array replaceObjectAtIndex:loopCount withObject:[NSString stringWithFormat#"%#.pdf", [name stringByReplacingOccurrencesOfString:#" " withString:#""]]];
}

Related

Create 1 million NSMutableArrays with unique names easily

After teaching myself (mostly from this website) I have finally been unable to find a solution to a problem.
I am trying to easily create 1 million NSMutableArrays with unique names. What I mean by easily is not having 'hard code' all of the individual arrays.
What I would like to do is something like this:
for (int i = 1; i <= 1000000; i++) {
NSString *arrayNumber = [NSString stringWithFormat:#"%d", i];
NSString *millionArrayNumber = #"millionArrayNumber";
NSString *arrayName = [millionArrayNumber stringByAppendingString:arrayNumber];
NSMutableArray *[NSString arrayName] = [NSMutableArray array];
}
I can understand why this doesn't work but I can't think of another way of doing it. I thought it might be possible to use something similar to:
[button setTag = 1];
If I change the code to:
for (int i = 1; i <= 1000000; i++) {
NSMutableArray *millionArray = [NSMutableArray array];
[millionArray setTag: i];
}
I would then use the tag to control the arrays as you can do with buttons. This doesn't work for arrays though.
I hope I haven't been ambiguous.

I'm not sure how to convert a string into literal code like you're doing, but I think it's possible.
However, you can always just kick 1 million arrays to an NSMutableDictionary and give each one your unique key name.
NSMutableDictionary *arrayStore = [NSMutableDictionary dictionary];
for (int i = 1; i <= 1000000; i++) {
NSString *arrayNumber = [NSString stringWithFormat:#"%d", i];
NSString *millionArrayNumber = #"millionArrayNumber";
NSString *arrayName = [millionArrayNumber stringByAppendingString:arrayNumber];
arrayStore[arrayName] = [NSMutableArray array];
}
And obviously to get whatever array you want later, you just use:
NSMutableArray *uniqueArray = arrayStore[arrayName];
Edit: Not sure if you want to keep the number as the unique key as mentioned in the comment below but if so, you can do it with this:
NSMutableDictionary *arrayStore = [NSMutableDictionary dictionary];
for (int i = 1; i <= 1000000; i++) {
arrayStore[#(i)] = [NSMutableArray array];
}
And access it with (for example, array number 100):
NSMutableArray *uniqueArray = arrayStore[#100];

Performance issue creating Section Index Titles for UITableView

I'm displaying an array of contacts ( [[ContactStore sharedStore]allContacts] ) in a tableview and have divided the list into alphabetic sections. I have used the following code to return an array of the first letters of the contacts, and a dictionary of the number of entries per letter.
//create an array of the first letters of the names in the sharedStore
nameIndex = [[NSMutableArray alloc] init];
//create a dictionary to save the number of names for each first letter
nameIndexCount = [[NSMutableDictionary alloc]init];
for (int i=0; i<[[[ContactStore sharedStore]allContacts]count]; i++){
//Get the first letter and the name of each person
Contact *p = [[[ContactStore sharedStore]allContacts]objectAtIndex:i];
NSString *lastName = [p lastName];
NSString *alphabet = [lastName substringToIndex:1];
//If that letter is absent from the dictionary then add it and set its value as 1
if ([nameIndexCount objectForKey:alphabet] == nil) {
[nameIndex addObject:alphabet];
[nameIndexCount setValue:#"1" forKey:alphabet];
//If its already present add one to its value
} else {
NSString *newValue = [NSString stringWithFormat:#"%d", ([[nameIndexCount valueForKey:alphabet] intValue] + 1)];
[nameIndexCount setValue:newValue forKey:alphabet];
}
}
This works, however it is very slow when the array is large, I'm sure there's a better way to do this but I'm quite new to this so am not sure how. Are there any suggestions for a better way to do this?

Although Bio Cho has a good point, you might see an increase in performance by calling
[[ContactStore sharedStore]allContacts]
only once. For example:
nameIndex = [[NSMutableArray alloc] init];
nameIndexCount = [[NSMutableDictionary alloc] init];
/*
Create our own copy of the contacts only once and reuse it
*/
NSArray* allContacts = [[ContactStore sharedStore] allContacts];
for (int i=0; i<[allContacts count]; i++){
//Get the first letter and the name of each person
Contact *p = allContacts[i];
NSString *lastName = [p lastName];
NSString *alphabet = [lastName substringToIndex:1];
//If that letter is absent from the dictionary then add it and set its value as 1
if ([nameIndexCount objectForKey:alphabet] == nil) {
[nameIndex addObject:alphabet];
[nameIndexCount setValue:#"1" forKey:alphabet];
//If its already present add one to its value
} else {
NSString *newValue = [NSString stringWithFormat:#"%d", ([[nameIndexCount
valueForKey:alphabet] intValue] + 1)];
[nameIndexCount setValue:newValue forKey:alphabet];
}
}
Though I can't say for sure, I'd guess that repeatedly accessing your shared store is what's killing you. Maybe only accessing it once will give you what you need.

Consider storing your contacts in Core Data and using an NSFetchedResultsController.
The NSFetchedResultsController will only load a subset of the rows which are visible on the table view, thus preventing your user from having to wait for all the contacts to be sorted.
NSFetchedResultsController will also sort your contacts by an attribute (ie. first or last name), and you can set your section titles to be the first letter of the field you're sorting by.
Take a look at this question and this tutorial.

How to create a comma-separated string?

I want to create a comma-separated string like this.
NSString *list = #"iPhone,iPad,iPod";
I tried like this,
[strItemList appendString:[NSString stringWithFormat:#"%#,", [[arrItems objectAtIndex:i]objectForKey:#"ItemList"]]];
But the issue is I'm getting a string like this
#"iPhone,iPad,iPod," Note that there is an extra comma "," at the end of the string. How can I avoid that extra comma?
Can you please give me a hint. Highly appreciated
Thanks in advance

To join an array of strings into a single string by a separator (character which would be a string), you could use this method of NSArray class:
NSArray* array = #[#"iPhone", #"iPad", #"iPod"];
NSString* query = [array componentsJoinedByString:#","];
By using this method, you won't need to drop the last extra comma (or whatever) because it won't add it to the final string.

There's a couple of routes you can take.
If the number of items is always the same, and known before hand (which I guess isn't the case, but I mention it for completeness's sake), just make the whole string at once:
[NSString stringWithFormat:#"%#,%#,%#", [[arrItems objectAtIndex:0] objectForKey:#"ItemList"]], [[arrItems objectAtIndex:1] objectForKey:#"ItemList"]], [[arrItems objectAtIndex:2] objectForKey:#"ItemList"]]
Knowing that the unwanted comma will always be the last character in the string, you can make removing it the last step in construction:
} // End of loop
[strItemList removeCharactersInRange:(NSRange){[strItemList length] - 1, 1}];
Or you can change your thinking a little and do the loop like this:
NSString * comma = #"";
for( i = 0; i < [arrItems count]; i++ ){
[strItemList appendString:[NSString stringWithFormat:#"%#%#", comma, [[arrItems objectAtIndex:i]objectForKey:#"ItemList"]]];
comma = #",";
}
Notice that comma comes before the other item. Setting that string inside the loop means that nothing will be added on the first item, but a comma character will be for every other item.

After Completion of loop add below stmt
strItemList = [strItemList substringToIndex:[strItemList length]-1]

check the value of array count if array count is last then add without comma else add with comma. try this out i am not sure to much about.
if([arrItems objectAtIndex:i] == arrItems.count){
[strItemList appendString:[NSString stringWithFormat:#"%#", [[arrItems objectAtIndex:i]objectForKey:#"ItemList"]]];
}
else {
[strItemList appendString:[NSString stringWithFormat:#"%#,", [[arrItems objectAtIndex:i]objectForKey:#"ItemList"]]];
}

Assuming that arrItems is an NSArray with elements #"iPhone", #"iPad", and #"iPod", you can do this:
NSArray *list = [arrItems componentsJoinedByString:#","]

NSArray with elements #"iPhone", #"iPad", and #"iPod"
NSString *str=[[arrItems objectAtIndex:0]objectForKey:#"ItemList"]]
str = [str stringByAppendingFormat:#",%#",[[arrItems objectAtIndex:1]objectForKey:#"ItemList"]]];
str = [str stringByAppendingFormat:#",%#",[[arrItems objectAtIndex:2]objectForKey:#"ItemList"]]];
NsLog(#"%#",str);

// Assuming...
NSDictionary *dictionary1 = [NSDictionary dictionaryWithObject:[NSArray arrayWithObjects:#"iPhone", #"iPodTouch", nil] forKey:#"ItemList"];
NSDictionary *dictionary2 = [NSDictionary dictionaryWithObject:[NSArray arrayWithObjects:#"iPad", #"iPad2", #"Apple TV", nil] forKey:#"ItemList"];
NSDictionary *dictionary3 = [NSDictionary dictionaryWithObject:[NSArray arrayWithObjects:#"iMac", #"MacBook Pro", #"Mac Pro", nil] forKey:#"ItemList"];
NSArray *arrItems = [NSArray arrayWithObjects:dictionary1, dictionary2, dictionary3, nil];
// create string list
NSString *strItemList = [[arrItems valueForKeyPath:#"#unionOfArrays.ItemList"] componentsJoinedByString:#", "];
NSLog(#"All Items List: %#", strItemList);
Output:
All Items List: iPhone, iPodTouch, iPad, iPad2, Apple TV, iMac, MacBook Pro, Mac Pro

This method will return you the nsmutablestring with comma separated values from an array
-(NSMutableString *)strMutableFromArray:(NSMutableArray *)arr withSeperater:(NSString *)saperator
{
NSMutableString *strResult = [NSMutableString string];
for (int j=0; j<[arr count]; j++)
{
NSString *strBar = [arr objectAtIndex:j];
[strResult appendString:[NSString stringWithFormat:#"%#",strBar]];
if (j != [arr count]-1)
{
[strResult appendString:[NSString stringWithFormat:#"%#",seperator]];
}
}
return strResult;
}

store each letter of NSString as object of NSMutableArray

I have an NSString of integer values. I need to add each one of the integers as a separate object in an NSMutableArray.
I tried characterAtIndex: but I keep getting errors…
P.s. I've solved over 30 problems thank's to stackoverflow's search, but didn't find any information on this problem.

NSMutableArray *results = [NSMutableArray array];
for (int i = 0; i < [string length]; i++)
{
NSString *substr = [string substringWithRange:NSMakeRange(i,1)];
[results addObject:[NSNumber numberWithInt:[substr intValue]];
}
NSLog(#" %# separated into: %#", string, results);

Consider looking at componentsSeparatedByString: or componentsSeparatedByCharactersInSet: for your purpose. Both methods are available on NSString.

If your integers are more than one digit or are space-separated, consider alternately using an NSScanner - you can read instances of NSInteger off the string one by one, wrap them in NSNumbers, and stick them in your array.

Filter a NSMutableArray index beyond bounds Problem

I am trying to filter a NSMutableArray. Search array for items by certain country. I have tried NSpredicate which works great however I need to re-use the original array which I cannot with NSpredicate. So I am trying the below code.
Q. What is the best way to filter an NSMutableArray keeping the original array intact?
//The following code works
filteredArray = [[NSMutableArray alloc] init];
unsigned int i;
for (i = 0; i < [appDelegate.arrayToBeFiltered count]; i++) {
id session = [appDelegate.ads objectAtIndex: i];
id Country = [[appDelegate.arrayToBeFiltered objectAtIndex: i] TheCountry];
[filteredArray addObject: session];
However when I add the if statement as below I get index beyond bounds
filteredArray = [[NSMutableArray alloc] init];
unsigned int i;
for (i = 0; i < [appDelegate.arrayToBeFiltered count]; i++) {
id session = [appDelegate.ads objectAtIndex: i];
id Country = [[appDelegate.arrayToBeFiltered objectAtIndex: i] TheCountry];
if (Country == #"United States"){
[filteredArray addObject: session];
}
}

Use - (NSArray *)filteredArrayUsingPredicate:(NSPredicate *)predicate
As a side-note, in the code above you probably mean to do this [Country isEqualToString: #"United States"]
As an extra side note - don't capitalise variables and method names. Just a style thing but capitalisation is usually reserved for Class names