Mastering Ruby Closures

Block Pattern #2: Managing Resources

Blocks are an excellent way to abstract pre- and post-processing. A wonderful example of that is resource management. Examples of resources that require extra care include file handles, socket connections, and database connections. For example, failure to close a database connection means that down the line, another connection attempt might be refused, since the number of connections that a database can handle is finite and limited.

Remembering to open and close the resource is a largely manual affair. This is error-prone and requires a bit of boilerplate. In the following example, the programmer is trying to open a file and write a few lines to it. The last line is where the programmer closes the file ...