Method Listen

Namespace

SodaFlow

Assembly

SodaFlow.dll

Listen<T>(Cell<T>, Action<T>)

Listen for updates to the value of this cell, without keeping the cell alive. The returned IWeakListener. A call to Unlisten() stops the listener, and the listener also stops when a GC collects it. This is an OPERATIONAL mechanism for interfacing between the world of I/O and FRP.

public static IWeakListener Listen<T>(this Cell<T> c, Action<T> handler)

Parameters

c Cell<T>

The cell.

handler Action<T>

The handler to run with each value.

Returns

IWeakListener

An IWeakListener. A call to its Unlisten() stops the listener. Only IStrongListener is also an IDisposable.

Type Parameters

T

The type of the cell.

Remarks

Make no assumption about the thread that calls the handler, and the handler must not block. The handler must not call Send<T>(StreamSink<T>, T) or Send<T>(CellSink<T>, T). They throw an exception, because this method is not for the definition of a new primitive.

With no call to Unlisten(), the listener continues. It stops when a GC collects the cell, or when a GC collects the listener.

This does not root the cell. Nothing here keeps the monitored graph in memory, thus the listener stops when a GC collects the cell. Keep the listener from this call where that matters, or use ListenStrong<T>(Cell<T>, Action<T>) to keep the cell in memory.