7. Initiating FileFlex Operations

FileFlex operates as a self-contained little world within the host environment. Each time you make a call to FileFlex, you're rapidly loading and unloading the FileFlex engine. But since FileFlex needs to maintain an awareness of all the database information between calls (when, normally, it would be completely out of the picture), FileFlex maintains it's own internal memory structures and data.

FileFlex also resides as an external code resource to your host environment. Before you can give FileFlex commands, you need to be able to establish communications with FileFlex. In most development environments, this is accomplished by opening a resource or opening an external library. In Director 5, this can be accomplished as easily as dropping the FileFlex Lingo Xtra into the Xtras folder (see the Installing FileFlex Files).

We've defined a special standard function for establishing this communication with FileFlex called DBInitPlatform. This function tells your host environment where to find FileFlex and how it should be called. It often requires you to write or customize a few lines in your native environment's language to open the resource. Details on defining DBInitPlatform are described in the FileFlex API Reference.

Once you've established communications, FileFlex must be initialized the first time it's used and "turned off" when you're finished. When you tell FileFlex to initialize itself, it allocates all the memory data structures it'll need for your database session. You'll need to call DBOpenSession for this to happen.

Warning: FileFlex is NOT reentrant. You may only call DBOpenSession once. Then, you can't call it again unless you've turned FileFlex off by calling DBCloseSession. Attempting to do repeated DBOpenSession or DBCloseSession calls without it's mate will result in very bad things happening.

After you are done using FileFlex, you should clean up your environment by releasing memory used for buffers. To do this, put the following call into the handler called when exiting your movie or project. (It may be placed elsewhere, but this is the most logical place for its use.)

  put DBCloseSession() into dbResult

This will free all the data structures in use by the FileFlex engine. Failure to do this may cause all sorts of unpleasant problems.

Finally, call DBClosePlatform to deallocate the external resource and turn off communications to FileFlex.

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