ios - 将属性从模态视图 Controller 传递给父级

Question

我有一个 tableview 作为父 View Controller 和一个子模态视图 Controller 。在模态视图 Controller 中，当用户点击一行时，我想设置父级的属性“过滤器”。但是，它只是返回 null。

如何将 NSString 过滤器属性传递回其父 View ？我应该在 didSelectRowAtIndexPath 方法中实例化父 View Controller 吗？

更新:使用 Delegates 解决，后跟 this tutorial .

下面是模态视图 Controller 的代码:

#import "FilterViewController.h"
#import "ContactsTableViewController.h"


@interface FilterViewController ()

@end

@implementation FilterViewController


- (void)viewDidLoad
{
    [super viewDidLoad];
    self.filterTable.dataSource = self;
    self.filterTable.delegate = self;
    [self performSelector:@selector(retrieveFilteredEvents)];
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.filterEvents count];
}

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

    static NSString *cellIdentifier = @"filterTableCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];


     NSDictionary *tempDict = [self.filterEvents objectAtIndex:indexPath.row];

    self.eventTitle = [tempDict objectForKey:@"eventType"];
    cell.textLabel.text = self.eventTitle;

    return cell;
}

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSDictionary *tempDict = [self.filterEvents objectAtIndex:indexPath.row];
    NSString *string = [tempDict objectForKey:@"eventType"];

    ContactsTableViewController *contactVC = [[ContactsTableViewController alloc] init];
    contactVC.filter = string;

    [self dismissViewControllerAnimated:YES completion:nil];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"updateParent" object:nil];
}

#pragma mark - Helper Methods

- (IBAction)done:(id)sender
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

-(void)retrieveFilteredEvents
{
    PFQuery *retrieveEvents = [PFQuery queryWithClassName:@"eventTypes"];
    [retrieveEvents orderByAscending:@"eventOrder"];
    [retrieveEvents findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
        if (!error) {
            self.filterEvents = [[NSArray alloc] initWithArray:objects];
        }
        [self.filterTable reloadData];
    }];

}

@end

Answer 1

有多种方法可以解决这个问题。我认为最简单的方法是在您的父类中设置一个属性，该属性会在您每次更新子类时更改。

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSDictionary *tempDict = [self.filterEvents objectAtIndex:indexPath.row];
    NSString *string = [tempDict objectForKey:@"eventType"];

    self.parentViewController.filter = string;

    [self dismissViewControllerAnimated:YES completion:nil];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"updateParent" object:nil];
}

另一种选择是使用代表。这可能是一个更清洁的解决方案，但对初学者不友好。

http://iosdevelopertips.com/objective-c/the-basics-of-protocols-and-delegates.html