NSArray *doc = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [doc[0] stringByAppendingPathComponent:@"my.db"];
NSURL *url = [NSURL fileURLWithPath:path];
原文：http://www.cnblogs.com/zhaozhongpeng/p/4867931.html