The value get by delegate method is been clear? - ios

Question

In tableViewControllerA.h I declare a delegate ,and in tableViewControllerA.m I implement the method when click a cell of the tableView, A will pass the value to B, and execute the perfromSegueWithIdentifier to jump to tableViewControllB,in tableViewControllB.m the getting method is called, and I get the value, but after the viewDidLoad() method call, the value become nil. Please help me to solve the problem.By the way , the property of the value is strong,nonatomic.
DTZHomeTableViewController.h
#import <UIKit/UIKit.h>
#import "PassData.h"
#protocol PassDataDelegate
-(void)passData:(PassData*) dataToProgram;
#end
#interface DTZHomeTableViewController :
UITableViewController<UITableViewDelegate,UITableViewDataSource>
#property(assign,nonatomic) id<PassDataDelegate> dataDelegate;
#end
PassData is an user-defined class
DTZHomeTableViewController.m
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
ProgramTableViewController *programViewController=
[[ProgramTableViewController alloc]init];
self.dataDelegate=programViewController;;
PassData *jump=[[PassData alloc]init];
jump.livingStatus=YES;
jump.role=0;
jump.index=indexPath.row;
jump.curOnlineNum=305605;
[self.dataDelegate passData:jump];
[self performSegueWithIdentifier:#"showSelectedProgram" sender:self];
}
ProgramTableViewController.h
#import <UIKit/UIKit.h>
#import "DTZHomeTableViewController.h"
#interface ProgramTableViewController :
UITableViewController<PassDataDelegate,UITableViewDataSource,UITableViewDelegate>
#property(strong,nonatomic) PassData * dataFromHome;
#end
ProgramTableViewController.m
#implementation ProgramTableViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"view did load%#",self.dataFromHome); // log :null
}
- (void) passData:(PassData *)dataToProgram
{
self.dataFromHome=dataToProgram;
}
#end

Answer 1

Delegation isn't the proper way to pass data to a segued view controller. Instead, you want to pass the data in prepareForSegue:sender:
Remove the protocol and delegate.
Add properties to your ProgramTableViewController for the data you want to pass.
#property (nonatomic, assign) BOOL livingStatus;
#property (nonatomic, assign) NSInteger role;
#property (nonatomic, assign) NSInteger row;
#property (nonatomic, assign) NSInteger curOnlineNum;
In prepareForSegue:sender:, set the ProgramTableViewController's passed properties to the values associated with the selected row:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)__unused sender
{
if ([[segue identifier] isEqualToString:#"showDetail"])
{
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
ProgramTableViewController *controller = (ProgramTableViewController *)[segue destinationViewController];
controller.livingStatus = YES;
controller.role = 0;
controller.row = indexPath.row;
controller.curOnlineNum = 305605;
}
}
You shouldn't allocate and init ProgramTableViewController in tableView:didSelectRowAtIndexPath:. Your segue will instantiate the destination view controller for you.
You don't even need to have a tableView:didSelectRowAtIndexPath: method. You can create a push segue from the tableViewCell to ProgramTableViewController, right within Storyboard. Give the segue an identifier (such as "showDetail"). Then in prepareForSegue, you assign the values, as I explained.
When you tap on that row, the segue will create a ProgramTableViewController, set the parameters, and present it for you.