Tag Creation

In its simplest form, the library create the tag string for logging implicitly. It is based on the class name that the log methods are invoked. The class name is transformed into abbreviated form for berevity of log output.

Why do we want to abbreviate the class name? The class name is usually long for any non-trivial app. Especially when the inner classes or Companion classes are involved. It may even exceed the tag length limit of 23 characters on pre Android N devices.

Essentially, the tag string is generated from the simple class name (i.e. regardless the package) by two rules:

Rule 1#

When there are not more than 2 capital characters in the name, then the tag is composed by taking each of the captial characters and the following small letter or digital, and keep the whole tag within 4 characters.. For example,

class name	tag
`HelloWorld`	`HeWo`
`Exception`	`Ex`
`MBone`	`MBo`
`AB123`	`AB1`

Rule 2#

When there are more than 2 capitals letters, only capital characters are extracted

class name	tag
`NullPointerException`	`NPE`
`ItIsAGoodDayToDie`	`IIAGDTD`

Additional Rule : Inner class and Companion class#

The tag for inner class is defined by combined by the abbreviation of the outer class name and the inner class name. E.g.

class name	tag
`HelloWorld.Listener`	`HeWoLi`
`View.OnClickListener`	`ViOCL`

Kotlin methods in companion object block are compiled to an inner class Companion within the outer class. IHLog make exception to the Companion class not including the "C" in abbreviation.

Meta tag#

We may specify a global prefix to the tag, known as "Meta Tag", so that all tags in the process is prepended with the meta tag. With meta tag, we can easily filter log output and focus on what is generated by our app. For example,

IHLogConfig.init(IHLogSetting(metaTagPolicy = SimpleMetaTag("MYAPP")))

class HelloWorld {
  fun hello() {
    l.debug("This is a log in class HelloWorld")
  }
}

class BananaOrange {
  fun apple() {
    l.debug("This is a log in class BananaOrange")
  }
}

The logcat output would be

03-03 02:04:49.949  1224  5126 D MYAPP_HeWo: This is a log in class HelloWorld
...
03-03 02:04:49.949  1224  5126 D MYAPP_BaOr: This is a log in class BananaOrange

By default the meta tag is empty string, and the underscore will not prepend tags.

Provide log tag explicitly#

We may also provide log tag explicitly for each log line.

l.debug("MyTag", "This is a log line with explicit log tag.")

// or

l.debug("MyTag") {
    "This is a log line with explicit log tag."
}