CommandPost Developer Guide
DownloadUser GuideFacebook Group
Search…
⌃K
Links

Statement

​
A Statement is defined to enable processing of asynchronous resolvable values such as cp.rx.Observable values.
To define a new Statement, you call the named constructor, assigning the result to a constant value and calling the define method.

Definine a new Statement

To define a new Statement implementation, we use the Statement.named constructor. This gives us a Statement.Definition which allows us to set the rules for the statement before finally "defining" it.
Statements may have an onInit, and must have an onObservable provided, and then the define method must be called.
For example, the First statement is defined like so:
local First = Statement.named("First")
:onInit(function(context, resolvable)
assert(resolvable ~= nil, "The First `resolveable` may not be `nil`.")
context.resolvable = resolvable
end)
:onObservable(function(context)
return toObservable(context.resolvable):first()
end)
:define()
Once you've defined a statement, you then execute it by calling the statement directly, passing in any parameters.
For example:
local First = require("cp.rx.go").First
First(Observable.of(1, 2, 3))
:Now(
function(value) print("Received: "..tostring(value)) end,
function(message) print("Error: "..tostring(message)) end,
function() print("Completed") end
)
This will output:
Received: 1
Completed
The Observable as passed to the onInit function handler as the second parameter. context is always the first parameter, followed by any values passed to the constructor call.
The onObservable function handler is called once the statement is actually executing, typically by calling the Now or After methods.
It is recommended that any conversion of input parameters are converted to Observables as late as possible, typically in the onObservable function handler. Otherwise, input values may get resolved before the user intends.

Submodules

API Overview

API Documentation

Functions

Signature
cp.rx.go.Statement.defaultObserverFactory([factoryFn]) -> nil
Type
Function
Description
Gets/sets the factory function which creates a new Observer for Statements which are executed without one being provided.
Parameters
  • factoryFn - if provided, replaces the current default factory function.
Returns
  • A new Observer, or the previous factory function if a new one was provided.
Notes
  • The factory function has no arguments provided and must return a new Observer instance.

​is​

Signature
cp.rx.go.Statement.is(thing) -> boolean
Type
Function
Description
Checks if the thing is a Statement.
Parameters
  • thing - The thing to test.
Returns
  • true if the thing is a Statement.
Signature
cp.rx.go.Statement.toObservable(thing[, params]) -> cp.rx.Observable
Type
Function
Description
Converts the thing into an Observable. It converts the following:
Parameters
  • thing - The thing to convert.
  • params - Optional table list to pass as parameters for the thing if it's a function.
Returns
  • The Observable.
Signature
cp.rx.go.Statement.toObservables(things[, params]) -> table
Type
Function
Description
Converts a list of things into a list of Observables of those things.
Parameters
  • things - a table list of things to convert to Observables.
  • params - an optional table list of parameters to pass to any function things.
Returns
  • A table list of the things, converted to Observable.

Constructors

​named​

Signature
cp.rx.go.Statement.named(name) -> Statement.Definition
Type
Constructor
Description
Starts the definition of a new Statement with the specified names.
Parameters
  • name - The name of the Statement.
Returns

Methods

​After​

Signature
cp.rx.go.Statement:After(millis[, observer][, scheduler]) -> nil
Type
Method
Description
Requests the statement to be executed after the specified amount of time in seconds.
Parameters
  • millis - The number of milliseconds to delay the execution.
  • observer - The observer to subscribe to the final result.
  • scheduler - (optional) the cp.rx.Scheduler to use. Uses the cp.rx.util.defaultScheduler() if none is provided.
Returns
  • Nothing.

​Catch​

Signature
cp.rx.go.Statement:Catch(handler) -> cp.rx.go.Statement
Type
Method
Description
Assigns a handler which will be applied at the end of the Statement.
Parameters
  • handler - The handler function
Returns
  • The same Statement.

​Debug​

Signature
cp.rx.go.Statement:Debug([label]) -> Statement
Type
Method
Description
Indicates that the results of the Statement should be output to the Error Log.
Parameters
  • label - If specified, this is output in the log.
Returns
  • The same Statement instance.

​Finally​

Signature
cp.rx.go.Statement:Finally(handler) -> Statement
Type
Method
Description
Provides a function handler to get called when the statement is done, either via an onError or onComplete signal.
Parameters
  • handler - The handler function.
Returns
  • The same Statement instance.

​fullName​

Signature
cp.rx.go.Statement:fullName()
Type
Method
Description
Returns the Statement's full name.
Returns
  • The full Statement name.

​Label​

Signature
cp.rx.go.Statement:Label(label) -> Statement
Type
Method
Description
Sets the custom label for the Statement. This will
Parameters
  • label - Optional new value for the label. If provided, the Statement is returned.
Returns
  • The Statement if a new lable is specified, otherwise the current label value.

​name​

Signature
cp.rx.go.Statement:name()
Type
Method
Description
Returns the Statement name.
Returns
  • The Statement name.

​Now​

Signature
cp.rx.go.Statement:Now([observer]) -> nil
Type
Method
Description
Executes the statment immediately.
Parameters
  • observer - An observer to watch the resulting Observable. Defaults to the default observer factory.
Returns
  • Nothing.

​ThenDelay​

Signature
cp.rx.go.Statement:ThenDelay(millis) -> cp.rx.go.Statement
Type
Method
Description
Indicates that there will be a delay after this statement by the
Parameters
  • millis - the amount of time to delay, in millisecods.
Returns
  • The same Statement.

​ThenYield​

Signature
cp.rx.go.Statement:ThenYield() -> cp.rx.go.Statement
Type
Method
Description
Indicates that the Statement will "yield" to allow other pending operations to happen,
Parameters
  • None
Returns
  • The same Statement.
Signature
cp.rx.go.Statement:TimeoutAfter(millis[, next][, scheduler]) -> cp.rx.go.Statement
Type
Method
Description
Indicates that this statement should time out after the specified number of milliseconds.
Parameters
  • millis - A number or a function returning the number of milliseconds to wait before timing out.
  • next - Optional string or resolvable value indicating how to handle it.
  • scheduler - The cp.rx.Scheduler to use when timing out. Defaults to cp.rx.defaultScheduler().
Returns
  • The same Statement.
Signature
cp.rx.go.Statement:toObservable([preserveTimer]) -> cp.rx.Observable
Type
Method
Description
Returns a new Observable instance for the Statement. Unless preserveTimer is true, this will
Parameters
  • preserveTimer - If a timer has been set via After, don't cancel it. Defaults to false.
Returns
  • The Observable.
CommandPost API - Previous
Retry
Next
Definition
Last modified 1yr ago