Media Center expression language-NEW

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Overview

The J. River Media Core database engine supports Excel-style functions for use in view schemes, searches, displayed columns, and tag editing.

An expression is a mixture of text, fields, and functions. A function allows special operations to be performed. Functions are all listed with a name followed by an opening and closing parenthesis. When building expressions, the instructions you wish to pass to the function are placed inside these parenthesis, with multiple instructions separated by commas. When your expression is evaluated, any spaces entered after a comma are ignored. This allows you to compose complex expressions on multiple lines, making it easier to keep track of where you are in your expression. Occasionally, you will find that you want a space, or parenthesis character to be treated literally as part of your instructions, rather than expression syntax, and in these cases, the character is "escaped" by using a preceding forward slash. As you progress with your expression building, you will begin nesting multiple functions into a single expression; always remember that a completed expression must contain a matching number of opening and closing parenthesis in order to work reliably.

The functions available to us range from highly functional, with a broad range of applicable uses, through specialised, limited use functions that only appeal to a select group of users, to seemingly redundant functions and obscure functions that MEDIA CENTER uses internally. The functions below are listed with those with the broadest appeal at the top, and the more obscure at the bottom.

Expressions can be used in many places within MEDIA CENTER, for varying reasons. Places that you might consider using expressions include:

  • The player information bar
  • The image playback caption
  • The "Rename, Move or Copy Files" tool
  • The tag window
  • Panes (aka categories)
  • List columns
  • Thumbnail text
  • The search field
  • The library field manager (Create expression based library fields)
  • Theatre View
  • The links manager (Use expressions to format the URLs for your links)

Fields

Any text between brackets [] will be replaced with the corresponding field from your library. As an example, [Artist] would be replaced by Bob Dylan for any Bob Dylan tracks. If the text between brackets doesn't match any known fields, it will be left alone. After the field name, a comma can be placed followed by a 0 or 1 for whether the field should get formatted. So, [Duration] and [Duration, 1] will give "4:02" while [Duration, 0] will give "242". This is particularly important when working with the "Format" functions, where most times you will want the evaluator to work with the raw field contents rather than the formatted contents you see in the file list.

All of this should become more clear if you study the examples offered below.

Functions

If(...): Outputs different values depending on the value of the first parameter.

Function Description Construction Examples
If() This will be the function you will likely use more than any other. It is typically used in conjunction with one or more other functions and allows you to give specific instructions depending upon whether the result is positive (1) or negative (0). The positive instruction is always given first. if(<expression to test>,<instructions if positive>,<instructions if negative>) if(isequal([artist],bob dylan),Genius,Mediocre)
==test== Cell B Cell C Cell D