iphone - 如何修复 Receiver in message expression is an uninitialized value warning

Question

对于创建 UIButton 的某些代码，我收到以下错误消息。我将如何初始化它以修复 Analyzer 警告我的错误:

逻辑错误:消息表达式中的receiver是一个未初始化的值

错误发生在粗体行

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UILabel *textLabel;
    UILabel *detailTextLabel;
    UIButton *button;

    UIFont *cellFont = [UIFont boldSystemFontOfSize:10.0];
    UIFont *detailCellFont = [UIFont fontWithName:@"Helvetica" size:8.0];

    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;

        // Initialize API title UILabel
        textLabel = [[[UILabel alloc] initWithFrame:CGRectZero] autorelease];
        textLabel.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleRightMargin;
        textLabel.tag = TITLE_TAG;
        textLabel.font = cellFont;
        [cell.contentView addSubview:textLabel];

        // Initialize API description UILabel
        detailTextLabel = [[[UILabel alloc] initWithFrame:CGRectZero] autorelease];
        detailTextLabel.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleRightMargin;
        detailTextLabel.tag = DESCRIPTION_TAG;
        detailTextLabel.font = detailCellFont;
        detailTextLabel.textColor = [UIColor blackColor];
        detailTextLabel.lineBreakMode = UILineBreakModeWordWrap;
        detailTextLabel.numberOfLines = 0;
        [cell.contentView addSubview:detailTextLabel];

        // Initialize API button UIButton
        button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        button.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleRightMargin;
        [button setBackgroundImage:[[UIImage imageNamed:@"blueButton.png"]
                                    stretchableImageWithLeftCapWidth:9 topCapHeight:9]
                          forState:UIControlStateNormal];
        [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [button addTarget:self action:@selector(apiButtonClicked:) forControlEvents:UIControlEventTouchUpInside];
        [cell.contentView addSubview:button];
    } else {
        textLabel = (UILabel *)[cell.contentView viewWithTag:TITLE_TAG];
        detailTextLabel = (UILabel *)[cell.contentView viewWithTag:DESCRIPTION_TAG];
        // For the button cannot search by tag since it is not constant
        // and is dynamically used figure out which button is clicked.
        // So instead we loop through subviews of the cell to find the button.
        for (UIView *subview in cell.contentView.subviews) {
            if([subview isKindOfClass:[UIButton class]]) {
                button = (UIButton *)subview;
            }
        }
    }

    CGSize constraintSize = CGSizeMake(280.0f, MAXFLOAT);

    // The API title
    NSString *cellText = [[apiMenuItems objectAtIndex:indexPath.row] objectForKey:@"title"];
    CGSize labelSize = [cellText sizeWithFont:cellFont
                            constrainedToSize:constraintSize
                                lineBreakMode:UILineBreakModeWordWrap];
    textLabel.frame = CGRectMake(20, 2,
                                 (cell.contentView.frame.size.width-40),
                                 labelSize.height);
    textLabel.text = cellText;

    // The API description
    NSString *detailCellText = [[apiMenuItems objectAtIndex:indexPath.row] objectForKey:@"description"];
    CGSize detailLabelSize = [detailCellText sizeWithFont:detailCellFont
                                        constrainedToSize:constraintSize
                                            lineBreakMode:UILineBreakModeWordWrap];
    detailTextLabel.frame = CGRectMake(20, (labelSize.height + 4),
                                       (cell.contentView.frame.size.width-40),
                                       detailLabelSize.height);
    detailTextLabel.text = detailCellText;


    // The API button
    CGFloat yButtonOffset = labelSize.height + detailLabelSize.height + 15;
    **button.frame = CGRectMake(20, yButtonOffset, (cell.contentView.frame.size.width-40), 44);**
    [button setTitle:[[apiMenuItems objectAtIndex:indexPath.row] objectForKey:@"button"]
            forState:UIControlStateNormal];
    // Set the tag that will later identify the button that is clicked.
    button.tag = indexPath.row;


    return cell;
}

谢谢你的帮助

Answer 1

您是否在代码中的任何地方做过类似的事情？

UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];

(类型也可能是 UIButtonRoundRect)

...或者这个:

UIButton* button = [[UIButton alloc] initWithType:UIButtonTypeCustom];