jpkessle commented on a change in pull request #3244: Move parameter docs to
separate page, add package params docs
URL:
https://github.com/apache/incubator-openwhisk/pull/3244#discussion_r165734620
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File path: docs/parameters.md
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@@ -0,0 +1,180 @@
+# Working with parameters
+
+### Passing parameters to an action at invoke time
+
+Parameters can be passed to the action when it is invoked. These examples use
JavaScript but all the other languages work the same way.
+
+1. Use parameters in the action. For example, update the 'hello.js' file with
the following content:
+
+ ```javascript
+ function main(params) {
+ return {payload: 'Hello, ' + params.name + ' from ' + params.place};
+ }
+ ```
+
+ The input parameters are passed as a JSON object parameter to the `main`
function. Notice how the `name` and `place` parameters are retrieved from the
`params` object in this example.
+
+2. Update the action so it is ready to use:
+
+ ```
+ wsk action update hello hello.js
+ ```
+
+3. Parameters can be provided explicitly on the command-line, or by supplying
a file containing the desired parameters
+
+ To pass parameters directly through the command-line, supply a key/value
pair to the `--param` flag:
+ ```
+ wsk action invoke --result hello --param name Dorothy --param place Kansas
+ ```
+
+ In order to use a file containing parameter content, create a file
containing the parameters in JSON format. The
+ filename must then be passed to the `param-file` flag:
+
+ Example parameter file called parameters.json:
+ ```json
+ {
+ "name": "Dorothy",
+ "place": "Kansas"
+ }
+ ```
+
+ ```
+ wsk action invoke --result hello --param-file parameters.json
+ ```
+
+ ```json
+ {
+ "payload": "Hello, Dorothy from Kansas"
+ }
+ ```
+
+ Notice the use of the `--result` option: it implies a blocking invocation
where the CLI waits for the activation to complete and then
+ displays only the result. For convenience, this option may be used without
`--blocking` which is automatically inferred.
+
+ Additionally, if parameter values specified on the command-line are valid
JSON, then they will be parsed and sent to your action as a structured object.
For example, if we update our hello action to:
+
+ ```javascript
+ function main(params) {
+ return {payload: 'Hello, ' + params.person.name + ' from ' +
params.person.place};
+ }
+ ```
+
+ Now the action expects a single `person` parameter to have fields `name` and
`place`. If we invoke the action with a single `person` parameter that is valid
JSON:
+
+ ```
+ wsk action invoke --result hello -p person '{"name": "Dorothy", "place":
"Kansas"}'
+ ```
+
+ The result is the same because the CLI automatically parses the `person`
parameter value into the structured object that the action now expects:
+ ```json
+ {
+ "payload": "Hello, Dorothy from Kansas"
+ }
+ ```
+
+### Setting default parameters on an action
+
+Actions can be invoked with multiple named parameters. Recall that the `hello`
action from the previous example expects two parameters: the *name* of a
person, and the *place* where they're from.
+
+Rather than pass all the parameters to an action every time, you can bind
certain parameters. The following example binds the *place* parameter so that
the action defaults to the place "Kansas":
+
+1. Update the action by using the `--param` option to bind parameter values,
or by passing a file that contains the parameters to `--param-file`
+
+ To specify default parameters explicitly on the command-line, provide a
key/value pair to the `param` flag:
+
+ ```
+ wsk action update hello --param place Kansas
+ ```
+
+ Passing parameters from a file requires the creation of a file containing
the desired content in JSON format.
+ The filename must then be passed to the `-param-file` flag:
+
+ Example parameter file called parameters.json:
+ ```json
+ {
+ "place": "Kansas"
+ }
+ ```
+
+ ```
+ wsk action update hello --param-file parameters.json
+ ```
+
+2. Invoke the action, passing only the `name` parameter this time.
+
+ ```
+ wsk action invoke --result hello --param name Dorothy
+ ```
+ ```json
+ {
+ "payload": "Hello, Dorothy from Kansas"
+ }
+ ```
+
+ Notice that you did not need to specify the place parameter when you invoked
the action. Bound parameters can still be overwritten by specifying the
parameter value at invocation time.
+
+3. Invoke the action, passing both `name` and `place` values. The latter
overwrites the value that is bound to the action.
+
+ Using the `--param` flag:
+
+ ```
+ wsk action invoke --result hello --param name Dorothy --param place
"Washington, DC"
+ ```
+
+ Using the `--param-file` flag:
+
+ File parameters.json:
+ ```json
+ {
+ "name": "Dorothy",
+ "place": "Washington, DC"
+ }
+ ```
+
+ ```
+ wsk action invoke --result hello --param-file parameters.json
+ ```
+
+ ```json
+ {
+ "payload": "Hello, Dorothy from Washington, DC"
+ }
+ ```
+
+### Setting default parameters on a package
+
+Parameters can be set at the package level, and these will serve as default
parameters for actions unless:
+
+- the action itself has a default parameter
Review comment:
The action itself has a default parameter.
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