ListSearcher

Categories

Strings

Searches a list to find a value and returns the index of the value in the list.

Example

For example, if this feature enters the transformer:

somelist{0}.length             = 7.3

somelist{0}.kind             = ’paved’

somelist{1}.length             = 8.4

somelist{1}.kind             = ’smooth’

somelist{1}.lanes             = 2

somelist{2}.length             = 1.1

somelist{2}.kind             = ’rough’

and the somelist{}.kind list attribute is searched for the value smooth, then the index attribute would be set to 1.

Output feature order may be controlled with the Advanced > Preserve Feature Order parameter.

Configuration

Output Ports

An element in the list matched. The output feature will return the index of the found element in the index attribute specified.

If the element is not found in the input feature, the feature will be output via this port and no index attribute will be applied.

Parameters

List Attribute

The name of the list to search. The list name should contain a pair of braces {}.

Search Type

This parameter determines how the list will be searched.

Parameter Choice Description

First Exact Match

Searches for an exact match.

First regular expression match

Uses a regular expression to search for a first matching entry in the list. Advanced Regular Expressions (AREs) are supported.

Advanced Regular Expressions (AREs) are supported. For a complete description of AREs, see Syntax of Perl-Compatible Regular Expressions at https://perldoc.perl.org/perlre#Regular-Expressions.

In brief, an ARE is one or more branches, separated by `|', matching anything that matches any of the branches.

First not matching

Returns the index of the first non-matched entry in the list.

First less than,
First less than or equal to,
First greater than,
First greater than or equal to

Searches for the first element in the list that satisfies the criteria. Numerical comparisons are used if both the list element and the search value can be converted to floating-point numbers; otherwise, string comparisons are used

Search For

The string or regular expression to search in the list.

If enabled, the contents of the found element will be copied to the main attribute(s) of the output feature. This saves adding a ListIndexer after the searcher to demote the list element.

Note that any list element attributes that start with fme_ will not be copied (for example, fme_type) unless you specify a Copied Attribute Prefix.

Copied Attribute Prefix

The prefix that should be added to any attribute(s) copied onto the output feature.

Preserve Feature Order

This parameter controls the order in which features exit a transformer.

When a transformer has more than one output port, features usually exit one port at a time. At times, it may be useful to keep the order that features arrived in, switching from port to port as necessary. This allows feature order to be preserved, though at a potential cost in processing efficiency.

Select a method for feature ordering.

Per Output Port (Default)

Only preserve the input order of features as they occur within the group of features exiting a given output port.

All features exiting an output port retain their ordering relative to each other (within the group), but not relative to features exiting other output ports.

This option is generally the most efficient, where large chunks of features will exit an output port together (taking advantage of bulk mode).

As features exiting different output ports may not be strictly output in the order they arrived, output ordering may be unpredictable.

Across Output Ports

Strictly preserve the input order of features, regardless of which output port they exit. Features will be output singly in the same order they arrived, switching from port to port as necessary. This option is generally less efficient as the processing gains of bulk mode are less likely to apply - however, feature order is predictable.

Matching List Index

If the Index Attribute is specified and the search string is found, an attribute with the specified name will be added to the output feature containing the index of the found element.

Additional Resources

More Information on Lists

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

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.

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.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

  • Add a row
  • Remove a row
  • Move current row up one
  • Move current row down one
  • Move current row to top
  • Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

  • Cut a row - delete and copy to clipboard
  • Copy a row to the clipboard
  • Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

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