TclCaller

Four Tcl global variables provide a gateway between an FME feature and the Tcl script: FME_FeatureType, FME_CoordSys, FME_AttrEncoding, and FME_AttrNameEncoding variables. In order to use these in a Tcl procedure, they must be declared as global; otherwise, the variables will be considered to be local and will not affect or interact with the FME feature upon which the function is run. To use them in a function, use a pattern like:

proc doSomething {

global FME_FeatureType

global FME_CoordSys

# rest of function goes here...

}

This global variable defines the name of the character encoding in which Tcl assumes a feature's attributes are specified when working with FME_GetAttribute and FME_SetAttribute functions. As Tcl works internally with UTF-8, this means that it will convert attribute values from the given encoding to UTF-8 when getting the value of attribute with FME_GetAttribute function, and will convert values from UTF-8 to the given encoding when setting the attribute value using FME_SetAttribute function.

The value of this variable does not impact the setting or retrieval of attributes when character encoding is known, either on the retrieved attribute or as directed by the arguments to FME_GetAttribute or FME_SetAttribute.

The default attribute encoding is the same as the default character encoding of the system on which FME is executing, and might be overridden by Tcl's built-in "encoding system" command. A complete list of supported encodings may be obtained by executing the command "encoding names".

The variable may be set, read, or unset:

set FME_AttrEncoding iso8859-2

puts $FME_AttrEncoding

unset FME_AttrEncoding

If FME_AttrEncoding is unset, or is set to be an empty string, it reverts to the default system encoding.

This function is used to determine if an attribute is present on a feature.

The syntax for FME_AttributeExists is:

FME_AttributeExists <attributeName>

<attributeName> is the name of the attribute whose value is to be retrieved.

If the attribute was present on the feature, the value 1 is returned; otherwise, 0 is returned.

This function is used to determine if the value of an attribute is null.

The syntax for FME_IsAttributeNull is:

FME_IsAttributeNull <attributeName>

<attributeName> is the name of the attribute whose value is to be checked.

If the attribute has a null value, the value 1 is returned; otherwise, 0 is returned.

This function is used to retrieve the names of all feature attributes and return them as a Tcl list.

The syntax for FME_AttributeNames is:

FME_AttributeNames

This global variable defines the name of the character encoding in which Tcl assumes a feature's attributes' names are specified when working with FME_GetAttribute and FME_SetAttribute functions. As Tcl works internally with UTF-8, this means that it will convert attribute names from UTF-8 to the given encoding system, and use the converted name when referring to the actual feature's attributes.

The default attribute encoding is the same as the default character encoding of the system on which FME is executing, and might be overridden by Tcl's built-in "encoding system" command. A complete list of supported encodings may be obtained by executing the command "encoding names".

The variable may be set, read, or unset:

set FME_AttrNameEncoding iso8859-2

puts $FME_AttrNameEncoding

unset FME_AttrNameEncoding

If FME_AttrNameEncoding is unset, or is set to be an empty string, it reverts to the default system encoding.

This global variable is set up to mirror the coordinate system of the feature. As with the FME_FeatureType variable, it can be set, read, and unset:

set FME_CoordSys UTM10-83

puts $FME_CoordSys

unset FME_CoordSys

In any Tcl procedure invoked by TclCaller, the FME_Coordinates function can be used to read and write the coordinates of the feature. It provides several options, as listed below:

dimension (2|3)

Sets the dimension of the feature - either 2 or 3.

numCoords

Returns the number of coordinates in the feature.

resetCoords

Removes all the current coordinates from the feature.

Note: Calling resetCoords has no effect on the fme_geometry or fme_type attributes. These must be reset or readjusted explicitly by the script so the feature is not left in an inconsistent state.

getCoord (x|y|z) <index>

Returns the coordinate value for the specified axis at the specified <index>.

<index> ranges from zero to one less than the number of coordinates.

addCoord <xvalue> <yvalue> [<zvalue>]

Adds the coordinate specified to the end of the feature's geometry.

geomType

Returns the geometry type of the feature - it will be one of the values allowed for the FME Geometry Model attributes:

fme_point

fme_line

fme_polygon

fme_donut

fme_aggregate

fme_undefined

geomType <type>

Sets the geometry type of the feature to the passed-in value. No sanity checking is done. It is important that this be done with care since setting an incorrect geometry type can later hinder FME.

This function is used to copy a feature attribute. The attribute's original internal data storage type is preserved by using this function. This can be significant when working with high precision floating-point values.

The syntax for FME_CopyAttribute is:

FME_CopyAttribute <newName> <oldName>

If the feature did not contain an attribute with the name oldName, then the function does nothing. It will not create a new blank valued attribute.

This function is used to decode character strings which have been encoded as described in the FME_EncodeText Function. The result of the function is a copy of the input parameter, with substituted string sequences converted back to the characters they represent.

The syntax for FME_DecodeText is:

FME_DecodeText <encodedText>

<encodedText> specifies a string which possibly contains substituted character string sequences.

This function is similar to FME_DecodeText, except that its argument may be interpreted as a reference to an attribute value rather than as a string to decode.

The syntax for FME_DecodeTextOrAttr is:

FME_DecodeTextOrAttr [&]<encodedText>

<encodedText> specifies a string which possibly contains substituted character strings.

If the argument begins with an ampersand character ("&"), the function returns the value in the attribute named by decoding the remainder of the argument. Otherwise, the function returns the decoded equivalent of <encodedText>.

This function is particularly useful when defining new transformers with GUI elements of "STRING_OR_ATTR_ENCODED" type.

This function is used to generate character strings which are encoded as described below in Substituting Strings in Mapping Files. The result of the function is a copy of the input parameter, with special characters converted to substituted string sequences which pass cleanly through FME's file parser, and can be represented in any ANSI character set.

The syntax for FME_EncodeText is:

FME_EncodeText <unencodedText>

<unencodedText> specifies the string which is to be encoded. Any special characters in this string will be replaced with the substitution sequences listed below.

Substituting Strings in Mapping Files

Occasionally, a character can cause a conflict in the mapping file parser. If this occurs, you can substitute safe character strings in many formats, functions and factories, including:

• Geodatabase writer (Attribute Definitions > subtypes, Attribute Definitions > domains)
• @Lookup
• PythonFactory
• @SearchList
• @SupplyAttributes
• @Tcl2

Character Substitutions

The encoding method is inspired by XML character entities.

Note: Substitutions are made only in attribute type definitions.

International Characters

The encoding described above takes care of characters that may cause problems with mapping file parsing, but it does interfere with some "special" characters from some encodings (where special means characters which are not a part of the 7-bit ASCII set.) The problems appear in systems where one or more bytes of a multibyte character are special to traditional encoding.

To counter this, FME supports Unicode-based character encoding. Encoding of the special characters is now done as a special tag, <uXXXX>, where XXXX is the hex representation for the UTF-16 character. This very simple encoding scheme is based on one observation (assumption): any characters which will cause problems inside of the encoding will involve one or more bytes which has the high bit set. Thus, in order to traditionally encode any string containing a character where a high bit is set, we have to convert the strings to a form where the encoding system is neutralized, where we can somehow represent that character with a string of bytes containing only 7-bit values (i.e. 7-bit clean values).

The encoding process basically applies the following heuristic:

If the string contains any bytes with the high bit set:

• Convert the string to UTF-16
• Convert the string 16-bit UTF-16 characters to a 7-bit traditionally encoded string

The outcome from this is an encoded string which is 7-bit clean (i.e., has no high bits set), and which can be decoded to get exactly the original characters for the unencoded result.

When encountering the character sequence <u anywhere within an encoded string, the decoder will be able to reverse the above process after a "traditional" decoding, to get back to the original UTF-8 or system-default encoded string.

If any 16-bit value is too large for a 7-bit character, replace it with \uXXXX, where XXXX is the hex representation for the 16-bit value.

Example

According to the encoding method, the attribute type

coded_domain(TextDom:char(50):a:"the letter a":b:"the letter b")

would be represented as

coded_domain(TextDom:char<openparen>50<closeparen>:a:

<quote>the<space>letter<space>a<quote>:b:<quote>the<space>

letter<space>b<quote>)

within a mapping file. Notice that the encoding is only applied to the body of the coded_domain type, i.e. coded_domain(<body>). Similarly, it would only be applied to the body of range_domain(<body>), subtype(<body>), and subtype_codes(<body>) which are Geodatabase attribute types and to enum(<body>) and set(<body>) which are both MySQL attribute types.

This function is used to call any FME function from within a Tcl procedure. This allows standard FME functions to be called iteratively on the same feature.

The syntax for FME_Execute is:

FME_Execute <functionName> [<arg1> ... <argN>]+

<functionName> is the name of any FME function, without the leading @ sign.

Any remaining arguments are passed to the function. For example, the @Generalize function is invoked like this:

FME_Execute Generalize Douglas 10

and this would accomplish the same effect as if @Generalize(Douglas,10) were invoked elsewhere in the mapping file.

If the function that is invoked causes the feature to be deleted, the translation will be aborted. The @Generalize function may do this if the feature's total length is less than the tolerance value passed in.

This global variable is set up to mirror the feature type of the feature. As with the other variables, it can be set, read, and unset:

set FME_FeatureType "Roadster"

puts $FME_FeatureType

This function can be used to get a value of attribute on the feature from within a Tcl procedure.

The syntax for FME_GetAttribute is:

FME_GetAttribute <attributeName> [<attributeEncoding>]

<attributeName> is the name of the attribute whose value is to be retrieved.

<attributeEncoding> is an optional character encoding used when interpreting the bytes of an existing attribute's value. If this is not specified, the bytes of an encoded attribute are interpreted according to their original encoding, and the bytes of a plain string attribute are interpreted according to the value of the FME_AttributeEncoding global variable.

If the attribute was not present on the feature, an empty string is returned as the value.

The FME_LogMessage function is used to write messages to the FME log file. It may be invoked in one of two ways:

FME_LogMessage <severity> <messageNumber> [<arg1> ... <argN>]+

or

FME_LogMessage <severity> <message>

<severity> can have one of these values: fme_inform, fme_warn, fme_error, fme_fatal, fme_statistic, and fme_statusreport

When the first form is used, the message number must be present in a file in the messages subfolder under the FME installation folder. The remaining parameters are used to fill in any %0, %1, ... %n parameter holders in the message. For example, if the message was:

3011, Opening file %0 for mode %1

then FME_LogMessage could be called like this:

FME_LogMessage fme_inform 3011 /tmp/cacher.txt read

In the second form, the message is output directly to the log file.

This function is used to rename a feature attribute. The attribute's original internal data storage type is preserved by using this function. This can be significant when working with high precision floating-point values.

The syntax for FME_RenameAttribute is:

FME_RenameAttribute <newName> <oldName>

If the feature did not contain an attribute with the name oldName, then the function does nothing. It will not create a new blank valued attribute.

This function is used to set the value of an attribute on a feature.

The syntax for FME_SetAttribute is:

FME_SetAttribute [-notranscode] <attributeName> <attrValue> [<attributeEncoding>]

<attributeName> is the name of the attribute whose value would be set to <attrValue>.

<attributeEncoding> is an optional character encoding to be applied to the resulting attribute. It overrides the effect of any value currently stored in the FME_AttributeEncoding global variable.

If the -notranscode option is specified, the bytes of the Tcl variable are copied verbatim to the resulting attribute, in place of a character encoding conversion from Tcl's internal UTF-8 encoding to the target character encoding. This is useful when the Tcl variable is known to contain an array of bytes in a particular character encoding instead of the usual sequence of UTF-8 characters.

The resulting attribute will normally have attached character encoding information. If the <attributeEncoding> argument is not specified, the attribute will default to a UTF-8 encoding unless the FME_AttributeEncoding global variable is defined. If this variable is defined, the resulting attribute will be an unencoded (plain string) attribute, with bytes representing the value's characters in the named encoding.

This function is used to set the value of an attribute on a feature to null. If the attribute does not exist, it will be created.

The syntax for FME_SetAttributeNull is:

FME_SetAttributeNull <attributeName>

<attributeName> is the name of the attribute whose value would be set to null.

If the attribute does not exist, it will be created and its type will be string.

This function generates a temporary filename in the FME temporary folder.

The filename is guaranteed to be a unique, new file.

Note: FME will create an empty file with the given name; you must delete it when you are done.

The syntax for FME_TempFilename is:

FME_TempFilename [<prefix>] [<suffix>]

If a prefix and suffix are not provided, the filename will be returned as an arbitrarily uniquely named file in the FME temporary folder. (For information on where this folder is located, see Temporary Folder Determination.)

If a prefix is provided, then that is used as the beginning portion of the filename within the temporary folder, and the suffix is used as the ending portion. Typically the suffix is used to append an extension, and in this case, it would have to additionally include a period "."

For example, this call:

FME_TempFilename raster .png

would return something like:

c:/Documents and Settings/username/Local Settings/Temp/rastera05921.png

This function is used to remove one or more attributes from a feature.

The syntax for FME_UnsetAttributes is:

FME_UnsetAttributes <attr1> [<attr2> <attr3 ...]

No error will be generated if the feature did not contain any of the attributes listed. FME_UnsetAttributes simply ignores any argument that does not specify an attribute on the feature.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters	Create your own editable parameters.

Note: Not all tools are available in all transformers.