当数组为空时，如何防止UITableView崩溃？

Question

When my app's user signs up for an account, the tableView starts out empty (as no data has been added by the user). How can I stop the app from crashing when the soon-to-be populated array is empty? So far, I've tried displaying a view when the table/array is empty, but the crash still occurs...

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{

    return [self.storageData count];

}

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    {
        static NSString *DoctorsTableIdentifier = @"StorageItemTableViewCell";

        StorageItemTableViewCell *cell = (StorageItemTableViewCell *)[tableView dequeueReusableCellWithIdentifier:DoctorsTableIdentifier];
        if (cell == nil)

            {
            NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"StorageItemTableViewCell" owner:self options:nil];
            cell = [nib objectAtIndex:0];
            }

        if (self.storageData > 0) {

            noitemsView.hidden = YES;

                NSDictionary *tmp = [self.storageData objectForKey:[NSString stringWithFormat:@"%d",(long)indexPath.row]];


            [[cell itemName] setText:(NSString *)[tmp objectForKey:@"title"]];

                  NSString *title = [tmp objectForKey:@"title"];
                  [[cell itemName] setText:title];


                NSDictionary *node = [self.descripData objectAtIndex:indexPath.row];
                [[cell itemDescrip] setText:[node objectForKey:@"body"]];
                NSLog(@"%@", self.descripData);

                NSString *secondLink = [[self.descripData objectAtIndex:indexPath.row] objectForKey:@"photo"];

                [cell.itemPhoto sd_setImageWithURL:[NSURL URLWithString:secondLink]];

                NSLog(@"%@",secondLink);


                  }   
        else {
            noitemsView.hidden = NO;
        } 
                  return cell;
                  }

Answer 1

You need to update your numberOfRows Delegate method

- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
   if ([self.storageData count] > 0 && self.descripData.count>0)
    {
      return [self.storageData count];
    }
     else
     return 1;
 }

Also modify the code as below

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
----------
        if (self.storageData.count > 0 && self.descripData.count>0) {
------------//Instead of self.storageData>0
        }
----------
}

It fixes the crash issue if storageData is empty..!

Answer 2

This is not really correct, but since your question is specifically about making the app not crash, you could do this:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (self.storageData)
        return [self.storageData count];
    else
        return 1;
}

This means that if the array is not empty, display the number of elements in the array. Else, display just 1 (or whatever default number you want).

Also, in cellForRowAtIndexPath, you need to make the same check:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *DoctorsTableIdentifier = @"StorageItemTableViewCell";

    StorageItemTableViewCell *cell = (StorageItemTableViewCell *)[tableView dequeueReusableCellWithIdentifier:DoctorsTableIdentifier];
    if (cell == nil)

        {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"StorageItemTableViewCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
        }

    if (self.storageData)   // <-- check for nil values first
        { if (self.storageData > 0) {
    //more code
    }

Again, not good or correct, but it makes the app not crash, which is what you asked about.

Answer 3

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
//If "numberOfRowsInSection" return '0' or nil, "cellForRowAtIndexPath" should not be called.
//Are you sure the "self.storageData.count" is empty?
if (_storageData == nil)
{
    return 0;
}
else
{
    return _storageData.count;
}
}

Answer 4

Here is a problem:

if (self.storageData > 0) {

        noitemsView.hidden = YES;
        ....

You are comparing self.storageData > 0 instead of [self.storageData count] > 0, so the if is always evaluating to true, and it is always trying to create a cell with data that is not available.

Answer 5

尝试以下方法。

self.tableView.dataSource = self.storageData ? self : nil;

Answer 6

鉴于确实写了代码

self.storageData = [[NSMutableArray alloc] init];

Answer 7

You need to check array count in number of row in section method: 1.

- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
 if(!myArray.count)
   return 0;

   return [myArray.count];
}