Scala-IO Core: To Resource Converters

In order to simplify integration with existing libraries, most commonly Java libraries, Scala-IO provides a JavaConverters object with implicit methods that add as*** methods (asInput, asOutput, asSeekable, etc...) to several types of objects.  It is the same pattern as in the scala.collection.JavaConverters object.

These methods can be used instead of the Resource.from*** methods to provide a slightly nicer appearing code.

There is one warning. When using JavaConverters, instead of Resource.from*** for creating Input/Output/Seekable/etc... objects, the chances of falling into the trap of creating non-reusable resources or causing a resource leak is increased. See: scala-io-core-reusable-resources for more details on this.

Scala-IO Core: ReadChars and WriteChars

The Input and Output objects of Scala-IO assume that the underlying data is composed of bytes.  However, another common pattern is to have the underlying data be composed of characters instead of bytes, for example java.io.Reader and java.io.Writer.  While it is possible to decompose the output into Bytes and construct an Input object from the decorated object, ReadChars and WriteChars can be used in this situation to reduce the work needed to interact with such resources.

ReadChars and WriteChars are traits that contain the character and string methods of Input and Output.  The primary difference is that the Charset is defined by the underlying resource rather than supplied at the method invocation site.  

Compare two methods:

Input:

def chars(implicit codec: Codec = Codec.default): LongTraversable[Char]

ReadChars:

def chars: LongTraversable[Char]

You will notice that the ReadChars method does not have the codec parameter because there translation is not required, unlike in Input which requires the characters to be created from raw bytes.

Not many examples are needed to explain these concepts but here are a few examples on how to create ReadChar and WriteChar objects: