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:
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local First = Statement.named("First")
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:onInit(function(context, resolvable)
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    assert(resolvable ~= nil, "The First `resolveable` may not be `nil`.")
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    context.resolvable = resolvable
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end)
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:onObservable(function(context)
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    return toObservable(context.resolvable):first()
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end)
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:define()
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Once you've defined a statement, you then execute it by calling the statement directly, passing in any parameters.
For example:
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local First = require("cp.rx.go").First
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First(Observable.of(1, 2, 3))
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:Now(
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    function(value) print("Received: "..tostring(value)) end,
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    function(message) print("Error: "..tostring(message)) end,
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    function() print("Completed") end
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)
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This will output:
1
Received: 1
2
Completed
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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
​cp.rx.go.Statement.Definition​
​cp.rx.go.Statement.Modifier​
API Overview
Functions - API calls offered directly by the extension
​defaultObserverFactory​
​is​
​toObservable​
​toObservables​
Constructors - API calls which return an object, typically one that offers API methods
​named​
Methods - API calls which can only be made on an object returned by a constructor
​After​
​Catch​
​Debug​
​Finally​
​fullName​
​Label​
​name​
​Now​
​ThenDelay​
​ThenYield​
​TimeoutAfter​
​toObservable​
API Documentation
Functions
​defaultObserverFactory​
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.
​toObservable​
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.
​toObservables​
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
A Statement.Definition.
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.
​TimeoutAfter​
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.
​toObservable​
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.