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What is the await-for agent method in Clojure?

Chinweuba Elijah Azubuike

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

Overview

Clojure variables are immutable. Still, we may use an agent to mutate the storage location alongside the use of functions. The changed state of the agent is then returned, as we'll see in the example below.

The await-for method sets a time delay of milliseconds to wait for the agent to be updated. After the set time is elapsed, the agent is then updated.

Syntax

(await-for time agentname)
Syntax of the await-for method

Parameters

The await-for method receives two parameters: the time and agentname, as shown above.

Return value

The return value of an await-for method is a boolean (True or False). It returns false due to timeout or a logical true for a successful update of the agent state.

(ns clojure.examples.example
(:gen-class))
(defn func []
(def names (agent 0))
(println @names)
(send-off names + 100)
(println (await-for 50 names))
(println @names)
(shutdown-agents))
(func)
An example of await-for menthod

Explanation

  • Line 3: We define a function func.
  • Line 4: We define a names variable with the agent method and we set the agent state to 0.
  • Line 5: We print the current state of the names variable which is 0
  • The names defined still remains a variable but to make it mutable we attach an agent. We attach an agent because by default all Clojure variables are immutable

  • Line 7: We use the send-off method to change the agent's state attached to the names variable. We change the names to 100; remember it was 0 initially.
  • Line 8: To enable the change to be updated to the names , we use the await-for method, which delays the program for 50 seconds and we print the output for the method, which gives a true .
  • Line 9: We print the names to ensure it was updated, giving us an updated value 100.
  • Line 10: We use the shutdown-agents to stop the agent from running. Read the shutdown-agents shot for better understanding.
  • Line 11: We call the function func.

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      clojure
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      CONTRIBUTOR

      Chinweuba Elijah Azubuike

      Grokking Modern System Design Interview for Engineers & Managers

      Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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