Why does my app crash when UISearchBar's textDidChange is called? - ios

Question

I have a UITableView which shows all of the songs in the Music Library, which works fine. However, when I start typing in the search bar to narrow down the search results, the app crashes immediately. Like as soon as I press one letter on the keyboard, it crashes. I've tried reworking my textDidChange: method but it always crashes, no matter what. I'm not sure what I'm doing wrong, could anyone help? Thanks.
Header:
#interface PTTableViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, UISearchBarDelegate>
#property (strong,nonatomic)UITableView* tableView;
#property (strong,nonatomic)UISearchBar* searchBar;
#end
ViewController.m:
#import "PTTableViewController.h"
#implementation PTTableViewController
MPMediaQuery *songsQuery;
NSArray *songsArray;
NSMutableArray *filteredArray;
NSMutableArray *songTitlesArray;
-(void)viewDidLoad{
[super viewDidLoad];
self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0,0,[UIScreen mainScreen].bounds.size.width - 75,150) style:UITableViewStylePlain];
self.tableView.dataSource = self;
self.tableView.delegate = self;
[self.view addSubview:_tableView];
self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0,0,320,44)];
self.searchBar.delegate = self;
self.searchBar.placeholder = #"Search";
self.tableView.tableHeaderView = self.searchBar;
songsQuery = [MPMediaQuery songsQuery];
songsArray = [songsQuery items];
songTitlesArray = [[NSMutableArray alloc] init];
for (MPMediaItem *item in songsArray) {
[songTitlesArray addObject:[item valueForProperty:MPMediaItemPropertyTitle]];
}
filteredArray = [[NSMutableArray alloc] init];
filteredArray = [songTitlesArray copy];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return filteredArray.count;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"cell"];
}
cell.textLabel.text = [filteredArray objectAtIndex:indexPath.row];
return cell;
}
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText{
NSLog(#"search changed");
[self performSelectorInBackground:#selector(helper) withObject:nil];
}
-(void)helper{
[filteredArray removeAllObjects];
if ([self.searchBar.text isEqualToString:#""]){
filteredArray = [songTitlesArray copy];
} else {
for (NSString *object in songTitlesArray){
if ([object rangeOfString:self.searchBar.text].location == NSNotFound){
NSLog(#"string not found");
} else {
NSLog(#"string found");
[filteredArray addObject:object];
}
}
} [self.tableView reloadData];
}
#end

Answer 1

First...
You're getting a crash because you do this:
filteredArray = [songTitlesArray copy];
Which assigns a non-mutable copy of songTitlesArray to filteredArray.
When you then try to do this:
[filteredArray removeAllObjects];
you're trying to mutate a non-mutable object.
You can fix this (first) problem in a couple ways...
One way is to change all instances of copy to mutableCopy:
filteredArray = [songTitlesArray mutableCopy];
However, using your exact code, you'll introduce new crashes because you'll be executing UI actions on a background thread.
Next... Are you sure you're getting "keyboard lag"?
You may want to change a few things:
make _filteredArray non-mutable
instead of calling removeAllObjects simply re-create the array
use filteredArrayUsingPredicate instead of looping through and comparing each string
Give this a try - because I don't have your MPMediaQuery I'll generate 500 strings as "song titles":
#interface PTTableViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, UISearchBarDelegate>
#property (strong,nonatomic)UITableView* tableView;
#property (strong,nonatomic)UISearchBar* searchBar;
#end
#implementation PTTableViewController
//MPMediaQuery *songsQuery;
NSArray *songsArray;
NSArray *filteredArray;
NSMutableArray *songTitlesArray;
-(void)viewDidLoad{
[super viewDidLoad];
self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0,0,[UIScreen mainScreen].bounds.size.width - 75,150) style:UITableViewStylePlain];
self.tableView.dataSource = self;
self.tableView.delegate = self;
[self.view addSubview:_tableView];
self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0,0,320,44)];
self.searchBar.delegate = self;
self.searchBar.placeholder = #"Search";
self.tableView.tableHeaderView = self.searchBar;
// songsQuery = [MPMediaQuery songsQuery];
// songsArray = [songsQuery items];
//
// songTitlesArray = [[NSMutableArray alloc] init];
// for (MPMediaItem *item in songsArray) {
// [songTitlesArray addObject:[item valueForProperty:MPMediaItemPropertyTitle]];
// }
// filteredArray = [[NSMutableArray alloc] init];
// filteredArray = [songTitlesArray copy];
// I don't have your Query, so let's create a 500 element string array,
// using the row number + one of the following words in each entry
NSString *samples = #"These are some random words for the song titles.";
// So, we'll have:
// "Row: 0 These"
// "Row: 1 are"
// "Row: 2 some"
// "Row: 3 random"
// "Row: 4 words"
// "Row: 5 for"
// "Row: 6 the"
// "Row: 7 song"
// "Row: 8 titles."
// "Row: 9 These"
// "Row: 10 are"
// "Row: 11 some"
// "Row: 12 random"
// "Row: 13 words"
// "Row: 14 for"
// ... etc
NSArray *a = [samples componentsSeparatedByString:#" "];
songTitlesArray = [[NSMutableArray alloc] init];
for (int i = 0; i < 500; i++) {
NSString *w = a[i % [a count]];
NSString *s = [NSString stringWithFormat:#"Row: %d %#", i, w];
[songTitlesArray addObject:s];
}
filteredArray = [songTitlesArray copy];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return filteredArray.count;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"cell"];
}
cell.textLabel.text = [filteredArray objectAtIndex:indexPath.row];
return cell;
}
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText{
[self helper];
}
-(void)helper{
if ([self.searchBar.text isEqualToString:#""]){
filteredArray = [songTitlesArray copy];
} else {
NSString *w = [NSString stringWithFormat:#"SELF contains[c] '%#'", self.searchBar.text];
NSPredicate *sPredicate = [NSPredicate predicateWithFormat:w];
filteredArray = [songTitlesArray filteredArrayUsingPredicate:sPredicate];
}
[self.tableView reloadData];
}
#end
As a side note, you've done a nice job of demonstrating one of the (many) reasons NOT to try and develop on a jailbroken device.