Return strings in sequence from NSMutableArray [closed] - objective-c

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Closed 9 years ago.
I have a NSMutableArray with comma separated strings for an objective-c iphone application (iOS SDK 6.0). I need a simple function that, when triggered, returns a string, one at a time, from string 0 onwards. To give you some context, a user would click a button, and for every click a new string is returned, in order, from the Array. It's a list of previously saved "favourite quotes". The string is displayed in a UITextView.
Ideally, I would also have a function for reversing, i.e. going backwards in the array from the current position.
This might be pretty basic, but I seem to only be able to find more advanced implementations that I'm unable to translate into this looping backwards and forwards in an Array of strings.
EDIT: Current code for this function below. I need to add the part where one string at a time is returned from the array (allRows) and displayed in a textview
- (IBAction)nextQoute:(id)sender {
const char *dbpath = [_databasePath UTF8String];
sqlite3_stmt *statement;
if (sqlite3_open(dbpath, &_qoutesDB) == SQLITE_OK)
{
NSString *querySQL = [NSString stringWithFormat:
#"SELECT qoutesSaved FROM qoutes"];
const char *query_stmt = [querySQL UTF8String];
if (sqlite3_prepare_v2(_qoutesDB,
query_stmt, -1, &statement, NULL) == SQLITE_OK)
{
NSMutableArray *allRows = [[[NSMutableArray alloc] init] autorelease];
while (sqlite3_step(statement) == SQLITE_ROW)
{
NSString *qouteField = [[NSString alloc]
initWithUTF8String:
(const char *) sqlite3_column_text(
statement, 0)];
NSString *str = [NSString stringWithFormat:#"%#", qouteField];
[allRows addObject:str];
[qouteField release];
}
Very thankful for help!

Answer 1

You mention that you are new to Objective C, and based on how I read what you're describing, I wonder if you are making this a lot more complicated than it needs to be. Items in an array (that is, NSArray, or NSMutableArray) aren't "seperated" by anything - different items in an array are accessed by their order in the array, called an index. So in your code, when you build allRows, each str that you put into it gets put into its own index, and to get it back out of the array, you just use that index.
For example, let's pretend your quotes you are pulling from your database are:
"Here's looking at you kid"
"I'll be back"
"It's a trap"
If they are put into the array in that order, and you want to put "It's a trap" into a textfield (called myTextField), you just write
myTextField.text = [allRows objectAtIndex:2];
In the end, that means what you probably want to do for your app is keep a counter you pass to objectAtIndex. When the user clicks the forward button, increase the count. When they click the back button, decrease the count. Then, call the code I put above, except instead of sending the value 2, send your counter variable. As mentioned in the comments to H2CO3s answer, make sure you put some validation in there to prevent your count from going beyond the limits of your array, or you'll get a nasty crash. If this is indeed what you are trying to do and you are still confused, I can add some more code.
I'm not too familiar with accessing a sqlite database the way you do here (I use CoreData, so the calls are very different), so perhaps I am completely mistaken about what you are trying to do here - but this seems like a very simple task that is being very overcomplicated.

Answer 2

You can just keep track of the string index in an instance variable (or if you don't have an object to work with because you write a class method or a function and not an instance method, then you can use a static local variable too).
#interface Foo: NSObject {
NSInteger index;
NSArray *strings;
}
// ...
- (NSString *)nextString
{
return index < strings.count ? strings[index++] : nil;
}
- (NSString *)previousString
{
return index > 0 ? strings[--index] : nil;
}

Answer 3

You can fetch the whole data in database.And store it one array
declare these two objects.
#interface YourClassName: NSObject {
NSInteger stringIndex;
NSArray *quoteFieldDataArr;
}
NSMutableArr *quoteFieldDataArr=[self fetchDataFromDataBase];
-(NSMutableDictionary *)fetchDataFromDataBase
{
const char *dbpath = [_databasePath UTF8String];
sqlite3_stmt *statement;
if (sqlite3_open(dbpath, &_qoutesDB) == SQLITE_OK)
{
NSString *querySQL = [NSString stringWithFormat:
#"SELECT qoutesSaved FROM qoutes"];
const char *query_stmt = [querySQL UTF8String];
if (sqlite3_prepare_v2(_qoutesDB,
query_stmt, -1, &statement, NULL) == SQLITE_OK)
{
NSMutableDictionary *allRows = [[[NSMutableDictionary alloc] init] autorelease];
while (sqlite3_step(statement) == SQLITE_ROW)
{
NSString *qouteField = [[NSString alloc]
initWithUTF8String:
(const char *) sqlite3_column_text(
statement, 0)];
NSString *str = [NSString stringWithFormat:#"%#", qouteField];
[allRows addObject:str];
[qouteField release];
return nil;
}
// Load Next String
- (NSString *)loadNextString
{
return stringIndex < quoteFieldDataArr.count ? quoteFieldDataArr[stringIndex++] : nil;
}
- (NSString *)loadpreviousString
{
return stringIndex > 0 ? quoteFieldDataArr[--stringIndex] : nil;
}