迅速使用FMDB-返回布尔值 [英] FMDB usage with swift - returning a boolean

问题描述

我目前正在快速构建一个使用FMDB与存储在设备上的数据库进行交互的应用程序.我选择使用FMDB，因为我有在Objective C上使用它的经验，并且它说它支持swift.

I am currently building an app in swift that uses FMDB to interact with a database that is stored on the device. I chose to use FMDB since I have experience using it with Objective C, and it says it supports swift.

我在执行语句时迅速返回布尔值时遇到问题.这是在Objective C类中使用FMDB时可以使用的更新功能的图像，请注意绝大多数用户是如何返回布尔值的

I am having problems with returning booleans in swift when executing a statement. Here is an image of the update functions available to me when using FMDB in an Objective C class, notice how the overwhelming majority return bools

以下是迅速提供的功能:

And here are the funcs available in swift:

没有给我太多帮助！

这是我当前在应用中使用的现有查询(名称已更改).

Here is an existing query I am currently using in an app (with names changed).

sql = @"INSERT INTO Table (IdValue, AnotherIDValue) VALUES (?, ?);";
BOOL success =  [db executeUpdate:sql,
                 [NSNumber numberWithLong:preference.idvalue1],
                 [NSNumber numberWithLong:preference.idvalue2],
                 nil];

该语句运行后，我将关闭数据库&返回布尔值.从本质上讲，这为我提供了一个完成块，并使我可以保持UI直到sql成功完成.

Once this statement runs I close off the database & return the boolean. This essentially gives me a completion block and lets me hold the UI up until the sql has successfully completed.

不幸的是，我的工作量大大减少了，而且我并不真正理解返回布尔值的函数输入.到目前为止，在我的快速数据库类中，我像这样运行更新:

Unfortunately with swift I have alot less to work with, and I don't really understand the function inputs that return bools. So far in my swift database class I run updates like so:

try! db.executeUpdate(sqlStatement, values: dataArray)

为我提供安全性(如果失败)，但是没有办法返回成功布尔值.我想知道是否有人像我在目标c中所示对实现数据库类有任何建议.

Giving me safety, if it fails, but no way to return a success boolean. I am wondering if anyone has any suggestions for implementing the database class like I showed in objective c.

我唯一看到的替代方法是在目标c中重写该类，但是我希望此应用程序保持100％快速运行.

The only alternative I can see is rewriting the class in objective c, however I would prefer to keep this app 100% swift.

推荐答案

来自在 将Swift与Cocoa和Objective-C一起使用"参考:

From Adopting Cocoa Design Patterns in the "Using Swift with Cocoa and Objective-C" reference:

Swift根据Swift的本机错误处理功能自动将产生错误的Objective-C方法转换为引发错误的方法.

Swift automatically translates Objective-C methods that produce errors into methods that throw an error according to Swift’s native error handling functionality.

因此，Objective-C方法

Therefore the Objective-C method

- (BOOL)executeUpdate:(NSString *)sql values:(NSArray *_Nullable)values error:(NSError *_Nullable __autoreleasing *)error

映射为

func executeUpdate(sql: String, values: [Any]?) throws 

转换为Swift，并且必须使用try的变体来调用.

into Swift, and must be called with (a variant of) try.

如果您仅对成功/失败状态感兴趣，而对 在实际的错误消息中(如您的目标代码)，然后 您可以使用try?，如果评估失败，则评估为nil:

If you are only interested in the success/failure status, but not in the actual error message (as in your Objective code), then you can use try?, which evaluates to nil if the evaluation failed:

let success = (try? db.executeUpdate(sqlStatement, values: dataArray)) != nil

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