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Class Latch

A latch that allows one task to wait until a value (object) has been provided by another task.
Inheritance
This class must not be extended.

Class summary

get -> any
Receives the value.
set value/any --exception/bool= -> none
Sets the value of the latch.
has-value -> bool
Whether this latch has already a value or an exception set.
operator == other/any -> bool
Whether this object is equal to the other.
stringify -> string
Stringifies this object.
await [condition] -> none
Yields until the condition block returns true.
try-await --deadline/int [condition] -> any
Yields until the condition block returns true or until the given deadline is reached.

Methods

await [condition] -> none
Yields until the condition block returns true.
This should be called from a locked method.
The condition is not allowed to change the state, only query it.
get -> any
Receives the value.
This method blocks until the value is available. If the value is an exception, it is thrown.
May be called multiple times.
has-value -> bool
Whether this latch has already a value or an exception set.
operator == other/any -> bool
Whether this object is equal to the other.
By default, identical is used for equality.
Inheritance
Classes overwrite this operator to get an equality specific to their needs. Equality operators often compare the type and field contents. For example:

class Pin:
  number/int

  constructor .number:

  operator == other:
    if other is not Pin: return false
    return number == other.number
A class doesn't have to follow the above format, but it must keep the operator in sync with any hash-code method. That is, if a class has a hash-code member, then the equality and hash-code must agree. If two instances are equal (a == b), then their hash codes must also be equal (a.hash-code == b.hash-code).
set value/any --exception/bool=false -> none
Sets the value of the latch.
Calling this method unblocks any task that is blocked in the get method of the same instance, sending the value to it.
Future calls to get return immediately and use this value.
If exception is true, the value is thrown in the task that calls the get method.
stringify -> string
Stringifies this object.
Inheritance
Objects that need a human-friendly string representation should overwrite this method. The default string is based on the internal class-ID.
try-await --deadline/int [condition] -> any
Yields until the condition block returns true or until the given deadline is reached.
Returns true if the condition has been met or false if we have reached the deadline.
This should be called from a locked method.
The condition is not allowed to change the state, only query it.