Unity Script Reference – MonoBehaviour.StartCoroutine

MonoBehaviour.StartCoroutine

function StartCoroutine (routine : IEnumerator) : Coroutine

Description

Starts a coroutine.

The execution of a coroutine can be paused at any point using the yield statement. The yield return value specifies when the coroutine is resumed. Coroutines are excellent when modelling behaviour over several frames. Coroutines have virtually no performance overhead. StartCoroutine function always returns immediately, however you can yield the result. This will wait until the coroutine has finished execution.

When using JavaScript it is not necessary to use StartCoroutine, the compiler will do this for you. When writing C# code you must call StartCoroutine.

JavaScript

// In this example we show how to invoke a coroutine and continue executing
// the function in parallel.

function Start() {
    // - After 0 seconds, prints "Starting 0.0"
    // - After 0 seconds, prints "Before WaitAndPrint Finishes 0.0"
    // - After 2 seconds, prints "WaitAndPrint 2.0"
    print ("Starting " + Time.time);
    // Start function WaitAndPrint as a coroutine. And continue execution while it is running

    // this is the same as WaitAndPrint(2.0) as the compiler does it for you automatically
    StartCoroutine(WaitAndPrint(2.0)); 
    print ("Before WaitAndPrint Finishes " + Time.time);
}

function WaitAndPrint (waitTime : float) {
    // suspend execution for waitTime seconds
    yield WaitForSeconds (waitTime);
    print ("WaitAndPrint "+ Time.time);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Start() {
        print("Starting " + Time.time);
        StartCoroutine(WaitAndPrint(2.0F));
        print("Before WaitAndPrint Finishes " + Time.time);
    }
    IEnumerator WaitAndPrint(float waitTime) {
        yield return new WaitForSeconds(waitTime);
        print("WaitAndPrint " + Time.time);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Start():
        print(('Starting ' + Time.time))
        StartCoroutine(WaitAndPrint(2.0F))
        print(('Before WaitAndPrint Finishes ' + Time.time))

    def WaitAndPrint(waitTime as single) as IEnumerator:
        yield WaitForSeconds(waitTime)
        print(('WaitAndPrint ' + Time.time))

Another Example:

JavaScript

// In this example we show how to invoke a coroutine and wait until it 
// is completed

function Start() {
    // - After 0 seconds, prints "Starting 0.0"
    // - After 2 seconds, prints "WaitAndPrint 2.0"
    // - After 2 seconds, prints "Done 2.0"
    print ("Starting " + Time.time);
    // Start function WaitAndPrint as a coroutine. And wait until it is completed.
    // the same as yield WaitAndPrint(2.0);
    yield StartCoroutine(WaitAndPrint(2.0));
    print ("Done " + Time.time);
}

function WaitAndPrint (waitTime : float) {
    // suspend execution for waitTime seconds
    yield WaitForSeconds (waitTime);
    print ("WaitAndPrint "+ Time.time);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    IEnumerator Start() {
        print("Starting " + Time.time);
        yield return StartCoroutine(WaitAndPrint(2.0F));
        print("Done " + Time.time);
    }
    IEnumerator WaitAndPrint(float waitTime) {
        yield return new WaitForSeconds(waitTime);
        print("WaitAndPrint " + Time.time);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Start() as IEnumerator:
        print(('Starting ' + Time.time))
        yield StartCoroutine(WaitAndPrint(2.0F))
        print(('Done ' + Time.time))

    def WaitAndPrint(waitTime as single) as IEnumerator:
        yield WaitForSeconds(waitTime)
        print(('WaitAndPrint ' + Time.time))

function StartCoroutine (methodName : String, value : object = null) : Coroutine

Description

Starts a coroutine named methodName.

In most cases you want to use the StartCoroutine variation above. However StartCoroutine using a string method name allows you to use StopCoroutine with a specific method name. The downside is that the string version has a higher runtime overhead to start the coroutine and you can pass only one parameter

JavaScript

// In this example we show how to invoke a coroutine using a string name and stop it

function Start () {
    StartCoroutine("DoSomething", 2.0);
    yield WaitForSeconds(1);
    StopCoroutine("DoSomething");
}

function DoSomething (someParameter : float) {
    while (true) {
        print("DoSomething Loop");
        // Yield execution of this coroutine and return to the main loop until next frame
        yield;
    }
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    IEnumerator Start() {
        StartCoroutine("DoSomething", 2.0F);
        yield return new WaitForSeconds(1);
        StopCoroutine("DoSomething");
    }
    IEnumerator DoSomething(float someParameter) {
        while (true) {
            print("DoSomething Loop");
            yield return null;
        }
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Start() as IEnumerator:
        StartCoroutine('DoSomething', 2.0F)
        yield WaitForSeconds(1)
        StopCoroutine('DoSomething')

    def DoSomething(someParameter as single) as IEnumerator:
        while true:
            print('DoSomething Loop')
            yield