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Unity Engine

StartCoroutine

Starts a coroutine named methodName.
Read time 3 minutesLast updated 4 days ago

Definition

  • Type: Method
  • Namespace: UnityEngine
  • Assembly: UnityEngine.CoreModule

StartCoroutine(string, Object)

Starts a coroutine named 
methodName
.
public Coroutine StartCoroutine(string methodName, object value)

Parameters

methodName

string

value

Object

Returns

Type

Description

Coroutine

Remarks

In most cases it's preferable to use the version of 
StartCoroutine
that accepts an 
IEnumerator
parameter, because it has lower runtime overhead. However, 
StartCoroutine
with a string 
methodName
lets you use MonoBehaviour.StopCoroutine with a specific method name.
// In this example we show how to invoke a coroutine using a string name and stop it.using UnityEngine;using System.Collections;public class ExampleClass : MonoBehaviour{    IEnumerator Start()    {        StartCoroutine(nameof(DoSomething), 2.0f);        yield return new WaitForSeconds(1);        StopCoroutine(nameof(DoSomething));    }    IEnumerator DoSomething(float someParameter)    {        while (true)        {            print("DoSomething Loop");            // Yield execution of this coroutine and return to the main loop until next frame            yield return null;        }    }}
A coroutine can start another coroutine and the two can interoperate in several ways, including both coroutines running in parallel. Alternatively, one coroutine can stop the other while it continues itself. In the following example, one coroutine pauses as it starts another one. When the second coroutine finishes, it restarts the first one.
using System.Collections;using System.Collections.Generic;using UnityEngine;public class ExampleClass : MonoBehaviour{    void Start()    {        StartCoroutine(coroutineA());    }    IEnumerator coroutineA()    {        // wait for 1 second        Debug.Log("coroutineA created");        yield return new WaitForSeconds(1.0f);        yield return StartCoroutine(coroutineB());        Debug.Log("coroutineA running again");    }    IEnumerator coroutineB()    {        Debug.Log("coroutineB created");        yield return new WaitForSeconds(2.5f);        Debug.Log("coroutineB enables coroutineA to run");    }}

StartCoroutine(IEnumerator)

Starts a coroutine.
public Coroutine StartCoroutine(IEnumerator routine)

Parameters

routine

IEnumerator

Returns

Type

Description

Coroutine

Remarks

The execution of a coroutine can be paused at any point using the 
yield
statement. When a 
yield
statement is used, the coroutine pauses execution and automatically resumes at the next frame. For more information, refer to Write and run coroutines in the manual.
Coroutines are useful for modeling behavior over several frames. The 
StartCoroutine
method returns upon the first 
yield return
, however you can also 
yield
the result, which waits until the coroutine has finished execution. There is no guarantee coroutines end in the same order they started, even if they finish in the same frame.
Yielding of any type, including 
null
, results in the execution coming back on a later frame, unless the coroutine is stopped or has completed. If the coroutine runs to completion without yielding (for example, if the 
yield
statement is unreachable), 
StartCoroutine
returns 
null
.
To stop a coroutine, use MonoBehaviour.StopCoroutine or MonoBehaviour.StopAllCoroutines().
Additional Resources: Coroutine, YieldInstruction

Examples

// This example invokes a coroutine and continues executing the function in parallel.using UnityEngine;using System.Collections;public class ExampleClass : MonoBehaviour{    private IEnumerator coroutine;    void 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.        coroutine = WaitAndPrint(2.0f);        StartCoroutine(coroutine);        print("Before WaitAndPrint Finishes " + Time.time);    }    // every 2 seconds perform the print()    private IEnumerator WaitAndPrint(float waitTime)    {        while (true)        {            yield return new WaitForSeconds(waitTime);            print("WaitAndPrint " + Time.time);        }    }}
// This example invokes a coroutine and waits until it is completed.using UnityEngine;using System.Collections;public class ExampleClass : MonoBehaviour{    IEnumerator 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 return WaitAndPrint(2.0f);        yield return StartCoroutine(WaitAndPrint(2.0f));        print("Done " + Time.time);    }    // suspend execution for waitTime seconds    IEnumerator WaitAndPrint(float waitTime)    {        yield return new WaitForSeconds(waitTime);        print("WaitAndPrint " + Time.time);    }}