- (BOOL) openDBFfile: (NSString *) filename;

This function opens DBF file. It accepts a string and returns a boolean value, true if everything was good.
Do not forget to close your file if you do not need it anymore.

{
    cdbfapi *dbf = [cdbfapi new];
    if ([dbf openDBFFile:@"./example.dbf"])
    {
        // your code
        [dbf closeDBFFile];
    }
    dbf = nil;
}