我正在創建一個登錄以查看支持票。第一個視圖是票證視圖，如果您未登錄，則將您帶到登錄屏幕。但是我收到這個：支持[3209：18e03] *由于未捕獲的異常'NSUnknownKeyException'而終止應用程序，原因：'[setValue：forUndefinedKey：]：此類不適用于鍵LoginScreen的鍵值編碼。*第一擲調用堆棧：（0x1f17012 0x1634e7e 0x1f9ffb1 0x10e1711 0x1062ec8 0x10629b7 0x108d428 0x7990cc 0x1648663 0x1f1245a 0x797bcf 0x65ce37 0x65d418 0x65d648 0x65d882 0x669235 0x8683d2 0x6664f3 0x666777 0x6667b7 0x9d1fe2 0x9c3ad9 0x65e422 0x2b15 0x65f753 0x65fb2f 0x661286 0x65fe3f 0x592910 0x592895 0x5926e5 0x1edfafe 0x1edfa3d 0x1ebd7c2 0x1ebcf44 0x1ebce1b 0x22aa7e3 0x22aa668 0x57c65c 0x1f0d 0x1e35）的libc + + abi.dylib：終止調用引發異常這是我的LoginScreen.m代碼#import "UIAlertView+error.h"#import "LoginScreen.h"#import "API.h"#include <CommonCrypto/CommonDigest.h>#define sayWhat @"REMOVEDFORSECURITY"@implementation LoginScreen-(void)viewDidLoad {    NSLog(@"Found me!");    [super viewDidLoad];    //focus on the username field /show keyboard    [fldUsername becomeFirstResponder];}- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation{        // Return YES for supported orientations        return (interfaceOrientation == UIInterfaceOrientationPortrait);    }    -(IBAction)btnLoginRegisterTapped:(UIButton*)sender {    if (fldUsername.text.length < 4 || fldPassword.text.length < 4){        [UIAlertView error:@"Enter username and password over 4 chars each."];        return;    }    //very basic encryption called "salting"    NSString* saltedPassword = [NSString stringWithFormat:@"%@%@", fldPassword.text, sayWhat];    //prep the hashed storage    NSString* hashedPassword = nil;    unsigned char hashedPasswordData[CC_SHA1_DIGEST_LENGTH];