PINView 介绍
PINView 让你实现加密解锁屏幕的操作，需要输入 4 个数字解锁码。
使用方法：
GCPINViewController *PIN = [[GCPINViewController alloc]
initWithNibName:nil
bundle:nil
mode:GCPINViewControllerModeCreate];
PIN.messageText = @"Create Passcode";
PIN.errorText = @"The passcodes do not match";
PIN.verifyBlock = ^(NSString *code) {
NSLog(@"setting code: %@", code);
return YES;
};
[PIN presentFromViewController:self animated:YES];
[PIN release];