Skip to contents

Report if JSON objects are used for input to and output from 'qgis_process'

Source: R/qgis-state.R
qgis_using_json_input.Rd

Returns a logical that reveals whether the JSON input and output methods are used, respectively.

Usage

qgis_using_json_input()

qgis_using_json_output(query = FALSE, quiet = TRUE)

Arguments

query

Logical. Should the outcome of qgis_using_json_output() ignore the cached value? The argument has effect on condition that no user setting 'use_json_output' is in place (see Details).

  • If set as TRUE, the function simply returns TRUE and the cached value for the current session is set as TRUE.

  • If set as FALSE (default), the function returns the cached value on condition that it does not conflict with a 'use_json_input' user setting.

quiet

Use FALSE to display more information, possibly useful for debugging.

Value

A logical of length 1.

Details

Since QGIS 3.24 the JSON input method of 'qgis_process' is used by default when calling the command. It allows to use certain algorithms that require a more complex input argument, e.g. a list of lists (see qgis_list_input()).

Likewise, JSON output is the default output format requested from 'qgis_process'. Using the JSON input method of 'qgis_process' automatically implies using the JSON output method; when not using the JSON input method it is possible (but not the default) to also not use the JSON output method.

The defaults can be overruled with the options qgisprocess.use_json_input or qgisprocess.use_json_output, and with the environment variables R_QGISPROCESS_USE_JSON_INPUT or R_QGISPROCESS_USE_JSON_OUTPUT.

The returned JSON output method is always cached during the current session by qgis_using_json_output(). Given that qgis_using_json_output() is called by various functions in the package, having a user setting 'use_json_output' in place (see above) will have effect during subsequent usage of the package. To cache the value between sessions, qgis_configure() needs to be called to update the value stored in the persistent package cache file.

The JSON input method is not cached but simply determined on the fly, based on QGIS version, the JSON output method and the user setting if present.

There is good reason for having 'use_json_output' in the persistent package cache: the values of qgis_algorithms() and qgis_plugins() are different with or without the JSON output method, and are also stored in the cache.

See also

Other topics about programming or debugging utilities: qgis_result_status(), qgis_run(), qgis_tmp_file(), qgis_unconfigure()

Other topics about reporting the QGIS state: has_qgis(), qgis_algorithms(), qgis_path()

Examples

qgis_using_json_input()
#> [1] TRUE
qgis_using_json_output()
#> [1] TRUE