Question

在UITableViewController中，在didSelectRowAtIndexPath下，我将NSObject文件中的属性设置为值。我可以使用NSLog，看看变量确实已经设置好了。但是，当我使用表视图并单击激活didSelectRowAtIndexPath的单元格时，我注意到当视图更改为另一个UITableViewController时，变量将自身设置为nil。我甚至在viewDidLoad下做了一个NSLog来检查这个属性值，它返回了nil。为什么是这样？我该怎么做才能让它自己变成零？

First UITableView.m：

#import "enchantmentViewController.h"
#import "levelViewController.h"
#import "dataBrain.h"

@interface enchantmentViewController ()

@property (nonatomic, strong) dataBrain *brain;
@property (nonatomic, strong) levelViewController *level;

@end

@implementation enchantmentViewController

@synthesize brain = _brain;
@synthesize level = _level;

- (dataBrain *)brain
{
    if (!_brain){
        _brain = [[dataBrain alloc] init];
    }
    return _brain;
}

- (levelViewController *)level
{
    if (!_level){
        _level = [[levelViewController alloc] init];
    }
    return _level;
}

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    //warning Potentially incomplete method implementation.
    // Return the number of sections.
    return [self.brain enchantmentNumberOfSections];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    //#warning Incomplete method implementation.
    // Return the number of rows in the section.
    return [self.brain enchantmentNumberOfCells:section];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    static NSString *CellIdentifier = @"enchantment";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (!cell) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
    }

    cell.textLabel.text = [self.brain enchantmentCellText:indexPath];

    return cell;

}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    return [self.brain enchantmentSectionData:section];
}


/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}
*/

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}
*/

/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    [self.brain convertSelectedTableCellToNumberOfPossibleEnchantments:indexPath];
    [self.brain test];
}

@end

第二个UITableViewController代码：

#import "levelViewController.h"
#import "dataBrain.h"

@interface levelViewController ()

@property (nonatomic, strong) dataBrain *brain;

@end

@implementation levelViewController

@synthesize brain = _brain;


- (dataBrain *)brain
{
    if (!_brain){
        _brain = [[dataBrain alloc] init];
    }
    return _brain;
}

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Table view data source

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

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    //NSLog(@"needing sections");

    NSLog(@"value: %@", [self.brain levelNumberOfCells]);
    return [self.brain.numberOfLevelsForCurrentEnchantment integerValue];
    //[self.brain levelNumberOfCells];

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"level";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (!cell) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
    }

    cell.textLabel.text = @"jo";//[self.brain levelCellText:indexPath];

    return cell;
}

@end

[self.brain test]返回有问题的变量的值。

Answer 1

因此每个viewController都有自己的大脑，在需要时会自动分配。你在一个VC的大脑中设置一个变量，然后切换VC，所以现在当你询问它的大脑时，你会问一个不同的大脑 - 你没有做过任何改变。

为什么我的变量设置为nil？

1 个答案: