launch.substitutions.string_join_substitution module

Module for the StringJoinSubstitution substitution.

class launch.substitutions.string_join_substitution.StringJoinSubstitution

Bases: Substitution

Substitution that joins strings and/or other substitutions.

This takes in a list of string components as substitutions. The substitutions for each string component are performed and concatenated, and then all string components are joined with a specified delimiter as seperation.

For example:

subdomain = LaunchConfiguration(variable_name='subdomain', default='docs')
url = StringJoinSubstitution(
    [['https', '://', subdomain], 'ros', 'org'],
    delimiter='.'
)

<launch>
    <arg name="subdomain" default="docs"/>
    <let name="url" value="$(string-join . https://$(var subdomain) ros org)"/>
</launch>

launch:
    - arg:
        name: subdomain
        default: "docs"
    - let:
        name: url
        value: "$(string-join . https://$(var subdomain) ros org)"

If the subdomain launch configuration was set to docs and the delimiter to ., then any of the above launch descriptions would result in a string equal to

'https://docs.ros.org'

__init__(substitutions: Iterable[str | Path | Substitution | Iterable[str | Path | Substitution]], delimiter: str | Path | Substitution | Iterable[str | Path | Substitution] = '') → None

Create a StringJoinSubstitution.

Parameters:

• substitutions – the list of string component substitutions to join

• delimiter – the text inbetween two consecutive components (default no text)

property delimiter: List[Substitution]

Getter for delimiter.

classmethod parse(data: Sequence[str | Path | Substitution | Iterable[str | Path | Substitution]]) → Tuple[Type[StringJoinSubstitution], Dict[str, Any]]

Parse StringJoinSubstitution substitution.

perform(context: LaunchContext) → str

Perform the substitution by retrieving the local variable.

property substitutions: List[List[Substitution]]

Getter for substitutions.