我希望我正在处理的程序的根视图控制器是一个PFQueryTableViewController，但是，我需要该应用程序来确保用户在PFQueryTableViewController尝试查询之前已登录。
我尝试创建一个RootTabBarViewController其初始视图为的PFQueryTableViewController并将以下内容放入RootTabBarViewController.h 和 .m 文件中：
//
// RootTabBarViewController.h
//
#import <UIKit/UIKit.h>
#import <Parse/Parse.h>
@interface RootTabBarViewController : UITabBarController <PFLogInViewControllerDelegate, PFSignUpViewControllerDelegate>
@end
//
// RootTabBarViewController.m
//
#import "RootTabBarViewController.h"
#import "PlannrLogInViewController.h"
@interface RootTabBarViewController ()
@end
@implementation RootTabBarViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
if (![PFUser currentUser]) { // No user logged in
// Create the log in view controller
PFLogInViewController *logInViewController = [[PFLogInViewController alloc] init];
[logInViewController setDelegate:self]; // Set ourselves as the delegate
// Create the sign up view controller
PFSignUpViewController *signUpViewController = [[PFSignUpViewController alloc] init];
[signUpViewController setDelegate:self]; // Set ourselves as the delegate
// Assign our sign up controller to be displayed from the login controller
[logInViewController setSignUpController:signUpViewController];
// Present the log in view controller
[self presentViewController:logInViewController animated:YES completion:NULL];
}
}
/*
#pragma mark - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
#pragma mark - PFLoginViewController Delegate
// Sent to the delegate to determine whether the log in request should be submitted to the server.
- (BOOL)logInViewController:(PFLogInViewController *)logInController shouldBeginLogInWithUsername:(NSString *)username password:(NSString *)password {
// Check if both fields are completed
if (username && password && username.length != 0 && password.length != 0) {
return YES; // Begin login process
}
[[[UIAlertView alloc] initWithTitle:@"Missing Information"
message:@"Make sure you fill out all of the information!"
delegate:nil
cancelButtonTitle:@"ok"
otherButtonTitles:nil] show];
return NO; // Interrupt login process
}
// Sent to the delegate when a PFUser is logged in.
- (void)logInViewController:(PFLogInViewController *)logInController didLogInUser:(PFUser *)user {
[self dismissViewControllerAnimated:YES completion:NULL];
}
// Sent to the delegate when the log in attempt fails.
- (void)logInViewController:(PFLogInViewController *)logInController didFailToLogInWithError:(NSError *)error {
NSLog(@"Failed to log in...");
}
// Sent to the delegate when the log in screen is dismissed.
- (void)logInViewControllerDidCancelLogIn:(PFLogInViewController *)logInController {
[self.navigationController popViewControllerAnimated:YES];
}
#pragma mark - PFSignUpViewController Delegate
// Sent to the delegate to determine whether the sign up request should be submitted to the server.
- (BOOL)signUpViewController:(PFSignUpViewController *)signUpController shouldBeginSignUp:(NSDictionary *)info {
BOOL informationComplete = YES;
// loop through all of the submitted data
for (id key in info) {
NSString *field = [info objectForKey:key];
if (!field || field.length == 0) { // check completion
informationComplete = NO;
break;
}
}
// Display an alert if a field wasn't completed
if (!informationComplete) {
[[[UIAlertView alloc] initWithTitle:@"Missing Information"
message:@"Make sure you fill out all of the information!"
delegate:nil
cancelButtonTitle:@"ok"
otherButtonTitles:nil] show];
}
return informationComplete;
}
// Sent to the delegate when a PFUser is signed up.
- (void)signUpViewController:(PFSignUpViewController *)signUpController didSignUpUser:(PFUser *)user {
[self dismissModalViewControllerAnimated:YES]; // Dismiss the PFSignUpViewController
}
// Sent to the delegate when the sign up attempt fails.
- (void)signUpViewController:(PFSignUpViewController *)signUpController didFailToSignUpWithError:(NSError *)error {
NSLog(@"Failed to sign up...");
}
// Sent to the delegate when the sign up screen is dismissed.
- (void)signUpViewControllerDidCancelSignUp:(PFSignUpViewController *)signUpController {
NSLog(@"User dismissed the signUpViewController");
}
@end
这是我的 PFQueryTableViewController 子类的 .m 文件：
//
// EventPFQueryTableViewController.m
//
#import "EventPFQueryTableViewController.h"
#import "Event.h"
@interface EventPFQueryTableViewController ()
@end
@implementation EventPFQueryTableViewController
- (id)initWithCoder:(NSCoder *)aDecoder{
self = [super initWithCoder:aDecoder];
if (self)
{
self.parseClassName = kEventListClassKey;
}
return self;
}
- (PFQuery *)queryForTable
{
PFQuery *query = [Event query];
[query whereKey:kEventListFieldKeyUser equalTo:[PFUser currentUser]];
return query;
}
/*
@end
但是，在加载（根栏视图控制器的第一个视图）并尝试查询viewDidLoad之前，此选项卡栏视图控制器的函数中的代码似乎没有运行，因为我仍然收到异常：PFQueryTableViewController
2014-07-10 20:46:04.226 Plannr [12810:60b] *由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“无法对类型进行比较查询：(null)”
我如何确保登录视图早于EventPFQueryTableViewController? 提前致谢。