objective-c - 由于 if/else 语句中的返回，Xcode 认为控制可能到达非空函数的结尾

Question

这是一个简单的问题:为什么下面的代码会导致“Control may reach end of-non-void function”警告？什么情况下两个 return 语句之一不会被命中？将第二个 return 语句放在 else block 之外是否是更标准的编码实践？这确实消除了警告，但我很好奇它为什么存在。

- (CGFloat) tableView: (UITableView *) tableView heightForRowAtIndexPath: (NSIndexPath *) indexPath
{
    NSString *lineToFit = [[self.fetchedResultsController objectAtIndexPath: indexPath] line];
    NSString *actorToFit = [[self.fetchedResultsController objectAtIndexPath: indexPath] actor];
    CGSize lineSize = [lineToFit sizeWithFont: [UIFont boldSystemFontOfSize: 12.0f] constrainedToSize: CGSizeMake(320, 800)];
    CGSize actorSize = [actorToFit sizeWithFont: [UIFont boldSystemFontOfSize: 12.0f] constrainedToSize: CGSizeMake(320, 800)];

    if (shouldDisplayExtra) {
        kExtraCellType cellType = [self cellIsGoingToContainExtraView];
        if (cellType != kExtraCellTypeNone) {
            [cellsToContainExtra setValue: [NSNumber numberWithInt: cellType] forKey: lineIDString];
            return lineSize.height + actorSize.height + 200;
        }
    } else {
        // Return the line height, actor height, plus a buffer.
        return lineSize.height + actorSize.height;
    }
}

Answer 1

您确实有导致无法返回的情况:

如果 shouldDisplayExtra 存在并且 cellType == kExtraCellTypeNone 则没有返回定义...

您应该在条件语句中添加一个 else block :

    if (cellType != kExtraCellTypeNone) {
        [cellsToContainExtra setValue: [NSNumber numberWithInt: cellType] forKey: lineIDString];
        return lineSize.height + actorSize.height + 200;
    } else {
       // return something here
    }