ios - 错误 : catch parameter is not a pointer to an interface type iOS

Question

我正在尝试在我的 Xcode 项目中使用异常处理。

- (void)viewDidLoad
{
    [super viewDidLoad];

    authenticate = [[UseDb alloc]init];
    @try{
    [authenticate createDatabase];
    }
    @catch (DatabaseCreationException) {
        NSLog(@"failed to create database");
    }
}

这是抛出异常的方法:

-(void)createDatabase
{

    NSString *docsDir;
    NSArray *dirPaths;
    char *sql_stmt1,*sql_stmt2,*sql_stmt3,*sql_stmt4;
    // Get the documents directory
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    docsDir = [dirPaths objectAtIndex:0];

    // Build the path to the database file
    _mDatabasePathDb = [[NSString alloc]
                     initWithString: [docsDir stringByAppendingPathComponent:
                                      @"SmartDiaryDatabaseTest2.sqlite"]];

    NSFileManager *filemgr = [NSFileManager defaultManager];

    if ([filemgr fileExistsAtPath: _mDatabasePathDb ] == NO)
    {
        const char *dbpath = [_mDatabasePathDb UTF8String];

        if (sqlite3_open(dbpath, &_mDb) == SQLITE_OK)
        {

            char *errMsg;

            sql_stmt1 = "CREATE TABLE IF NOT EXISTS USERDETAIL (mUserName TEXT PRIMARY KEY, mPassword TEXT,mUname TEXT, mImage TEXT, mGender CHAR, mDob DATE, mEmail TEXT, mAddress TEXT, mMaritalStatus BOOL, mLatitude DOUBLE, mLongitude DOUBLE)";

            if (sqlite3_exec(_mDb, sql_stmt1, NULL, NULL, &errMsg) != SQLITE_OK)
            {

            }

            sql_stmt2 = "CREATE TABLE IF NOT EXISTS CONTACTS (mName TEXT, mContactno TEXT, mCgender CHAR, mCdob DATE, mCemail TEXT, mClatitude DOUBLE, mClongitude DOUBLE)";

            if (sqlite3_exec(_mDb, sql_stmt2, NULL, NULL, &errMsg) != SQLITE_OK)
            {
                NSLog(@"failed to create table");

            }

            sql_stmt3 = "CREATE TABLE IF NOT EXISTS TODO (mStartDate DATE, mEndDate DATE, mTaskName TEXT, mTaskDescription TEXT, mPriority INT)";

            if (sqlite3_exec(_mDb, sql_stmt3, NULL, NULL, &errMsg) != SQLITE_OK)
            {
                NSLog(@"failed to create table");
            }


            sql_stmt4 = "CREATE TABLE IF NOT EXISTS FAVORITES (mTdate DATE, mNewsLabel TEXT )";

            if (sqlite3_exec(_mDb, sql_stmt4, NULL, NULL, &errMsg) != SQLITE_OK)
            {

            }
           // sqlite3_close(_mDb);

        } else {
            NSLog(@"failed to create database");
            NSException *e = [DatabaseCreationException exceptionWithName:@"DatabaseCreationFailedException" reason:@"sqlite execution failed" userInfo:nil];
            @throw e;

        }

    }
    sqlite3_close(_mDb);
}

我收到问题中提到的错误:catch parameter is not a pointer to an interface type iOS 我第一次在 Objective C 中处理异常。请告诉我我在哪里我错了。我创建了一个名为 DatabaseCreationException 的新类并将其导入。

Answer 1

你需要通过指针来捕获异常，像这样:

@try{
    [authenticate createDatabase];
}
@catch (DatabaseCreationException*ex) {
//                               ^
    NSLog(@"failed to create database");
}

请注意，Apple 强烈建议不要使用异常来处理运行时情况，将它们保留在应用程序即将关闭的情况下(即不可恢复的情况)。如果情况可以恢复，Apple 建议使用 NSError ( Exceptions Programming Guide )。