Question

我真的很难弄清楚为什么我的一个委托方法表现完美，但另一个不会。以下是代理的相关代码：

SideBarController.h

#import <UIKit/UIKit.h>
#import "Report.h"

@protocol ReportSelectViewControllerDelegate <NSObject>
@optional
    - (void) viewSelectMonitoredArea:(Report *)report;

@end

@interface SidebarController : UIViewController <UITableViewDataSource, UITableViewDelegate>

@property (nonatomic, weak) id <ReportSelectViewControllerDelegate> delegate;
@property (nonatomic, weak) IBOutlet UITableView *tableView;
@property (nonatomic, weak) Report *selectedReport;

@end

SideBarController.m

#import "SidebarController.h"

@interface SidebarController ()

@end

@implementation SidebarController

@synthesize tableView = _tableView;
@synthesize delegate;

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    NSMutableArray *sectionArray = [self.tableViewItems objectAtIndex:indexPath.section];
    NSDictionary* item = sectionArray[indexPath.row];

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:item[@"title"] forKey:@"CurrentReportTitle"];

    self.selectedReport = [Report where:@{@"reportTitle": item[@"title"]}].lastObject;

    [self.delegate viewSelectMonitoredArea:self.selectedReport];

    [tableView deselectRowAtIndexPath:indexPath animated:YES];

}

DetailReportViewController.h

#import <UIKit/UIKit.h>
#import "BDBSplitViewController.h"
#import "SidebarController.h"

@interface DetailReportViewController : BDBDetailViewController <UISplitViewControllerDelegate, ReportSelectViewControllerDelegate >

@end

DetailReportViewController.m

#import "DetailReportViewController.h"

@interface DetailReportViewController ()

@end

@implementation DetailReportViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    SidebarController *sideBarController = [[SidebarController alloc] init];
    sideBarController.delegate = self;
}

- (void) viewSelectMonitoredArea:(Report *)report {

    NSLog(@"viewSelectMonitoredArea was called");
}

从另一个控制器到DetailReportViewController以完全相同的方式编写的另一个委托工作正常。当我在调用委托后立即设置断点时，我注意到委托的值为nil。任何帮助将不胜感激。修改抱歉，我忘记在DetailReportViewController.h示例中输入sideBarController.delegate = self。它在原始代码中。

Answer 1

DetailReportViewController类需要获取对“SideBarController”实例的引用，然后将自己设置为委托。在DetailReportViewController中：

// This needs to be in the DetailReportViewController class
// Assume we have a reference to the SideBarController in the DetailReportViewController class called sideBarControllerInstance
sideBarControllerInstance.delegate = self;

Answer 2

迈克尔·道特曼推动的解决方案是

DetailReportViewController *detailReport = [[DetailReportViewController alloc] init];
    self.delegate = detailReport;

之前

[self.delegate createSelectMonitoredArea:self.selectedReport];

谢谢！

委托方法未执行

2 个答案: