Getting Started with Tcl in FME: AttributeCreator

Previous: TclCaller

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2015-02-22 Note: The @Evaluate function of FME 2015 will not return non-numeric value any longer. If the Tcl expression which is embedded to the argument for the function returns non-numeric, the @Evaluate functions will return <null>. Therefore, the following examples are unavailable in FME 2015 unfortunately.
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Tcl commands can be embedded in a "Value" parameter of the AttributeCreator transformer; for example:
@Evaluate([string toupper {@Value(attr_name)}])
- Source: Evaluate Tcl Commands in AttributeCreator
- Destination: EVALUATE TCL COMMANDS IN ATTRIBUTECREATOR
Tcl Commands > string toupper

@Value function puts an existing attribute value specified by its name, @Evaluate function evaluates Tcl commands within brackets and returns the result value.
On the Arithmetic Editor, we don't need to type "@Evaluate" and outer brackets. Write only Tcl commands bracketed by "[ ... ]", it will be bracketed with "@Evaluate(...)" automatically after closing the editor.

Several examples from the Community:

RegEx for finding more than one letter in a string
@Evaluate([regsub -all {[^A-Z]+} {@Value(attr1)} {}])
- Source: Apples Bananas Cherries
- Destination: ABC
Tcl Commands > regsub

Sort only part of an attribute in a list
@Evaluate([regsub {(.+)_(.+)} {@Value(attr2)} {\2_\1}])
- Source: 34N27W_100700
- Destination: 100700_34N27W

Regular Expression evaluation
@Evaluate([join [regexp -all -inline -- {[^0-9]+[0-9]+} {@Value(attr3)}] {,}])
- Source: F29920110716104845F37920120929203346TC20080508184800
- Destination: F29920110716104845,F37920120929203346,TC20080508184800
Tcl Commands > join, regexp

StringReplace to find multiple attributes
@Evaluate([string map {Red Stop Green Go Blue Other} {@Value(attr4)}])
- Source: Green
- Destination: Go
Tcl Commands > string map

Attribute Trimmer
@Evaluate([
array set s [regsub {^(.+)(...)$} {@Value(attr5)} {front {\1} back {\2}}]
return $s(front)[format {%03d} [expr [string trimleft $s(back) {0}] + 1]]
])
- Source: 4VK012
- Destination: 4VK013
TclCommand > array, format, expr, string trimleft, return

Also multiple command lines are acceptable like the example above.
Note: Since Tcl interpreter will try to interpret a string starting with 0 (zero) as an octal number when performing arithmetic processing, we should trim leading zeros if the string have to be interpreted as a decimal number.

Although, of course, these examples can be replaced with existing transformers, the AttributeCreator with Tcl commands could be useful to prevent a cluttered workspace when many string operations have to be performed simultaneously.

Next: Other Transformers