Custom transforms

Implementing your own transform

Perhaps the default transformation, DefaultTransform, may not be what you want. Maybe you want the module name included in the logged messages or perhaps don't want the date-and-timestamp included at all. All of this can be up to you if you choose to implement your own message transform.

You will need to start off with a class that inherits from the MessageTransform class and then which overrides the transform method as shown below:

import dlog;

public class CustomTranform : MessageTransform
    public override string transform(string text, Context context)
        string transformed;

        /* Insert code to transform `text` and return the `transformed` text */

        return transformed;

Additional information, besides the text being logged itself (this is the string text argument), comes in the form of a Context object context. What one can get from this is a CompilationInfo struct which contains the following fields below if one calls toArray() on it which will return a string array shown below (we refer to this array as lineInfo):

  1. lineInfo[0]
    • This contains __FILE_FULL_PATH__ which is the full path (absolute) to the source file where log() was called
  2. lineInfo[1]
    • This contains __FILE__ which is the path (starting at source/ to the source file where log() was called
  3. lineInfo[2]
    • This contains a stringified version of __LINE__ which is the line number of the call to log()
  4. lineInfo[3]
    • This contains __MODULE__ which is the name of the module the call to log() appeared in
  5. lineInfo[4]
    • This contains __FUNCTION__ which is the name of the function log() was called in
  6. lineInfo[5]
    • This contains __PRETTY_FUNCTION__ which is the same as above but with type information

The point of a Context object is also such that a custom transformer may expect a kind-of Context like a custom one (i.e. CustomContext) which perhaps a custom logger (kind-of Logger) can then have set certain fields in it.

Creating a Logger

We now need to create a logger that makes use of our message transform, we can do so by creating an instance of the Logger class and passing in our MessageTransform as so:

Logger customLogger = new DefaultLogger(new CustomTranform());

The above is all one needs to be able to pull off a custom transformation.