测试一：使用member function创建action会产生gc，不管该函数是否访问外部变量：
private System.Action memberAct = null;
// gc 112B
private void ActionWithMethod()
{
memberAct = new System.Action(LocalMethod);
}
// gc 112B, if LocalMethod() is static, then no gc
private void ActionWithMethod2()
{
memberAct = LocalMethod;
}
// no gc
private void ActionWithMethod3()
{
System.Action act = memberAct;
}
private void LocalMethod()
{
foreach (var item in lst)
Debug.Log(item);
}
ActionWithMethod和ActionWithMethod2是等效的，gc值如下所示：
IL代码也一摸一样：
所以将一个member function复制给一个action会产生gc，解决的办法就是ActionWithMethod3，也就是用一个actin member缓存起来，然后将缓存的action member复制给新建的action，这样只会产生一次gc:
如果将LocalMethod设置为static函数，则ActionWithMethod2也不会产生gc:
private static void LocalMethod()
{
}
测试二：使用匿名函数，如果访问了外部变量，也会产生gc；如果不访问外部变量，则只产生一次gc
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class TestAnonymousFunctionGC : MonoBehaviour
{
private System.Action actMember = null;
private int iMember = ;
public TestAnonymousFunctionGC()
{
}
private void Update()
{
UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithoutArg ***");
AnoymousFunctionWithoutArg();
UnityEngine.Profiling.Profiler.EndSample();
UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithMemberArg ***");
AnoymousFunctionWithMemberArg();
UnityEngine.Profiling.Profiler.EndSample();
UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg1 ***");
AnoymousFunctionWithLocalArg1();
UnityEngine.Profiling.Profiler.EndSample();
UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg2 ***");
AnoymousFunctionWithLocalArg2();
UnityEngine.Profiling.Profiler.EndSample();
UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg3 ***");
AnoymousFunctionWithLocalArg3();
UnityEngine.Profiling.Profiler.EndSample();
}
// no gc
private void AnoymousFunctionWithoutArg()
{
actMember = () => { };
}
// gc 112B
private void AnoymousFunctionWithMemberArg()
{
actMember = () =>
{
Debug.Log(iMember);
};
}
// gc 129B
private void AnoymousFunctionWithLocalArg1()
{
bool bValue = true;
actMember = () =>
{
Debug.Log(bValue);
};
}
// gc 132B
private void AnoymousFunctionWithLocalArg2()
{
int iValue = ;
actMember = () =>
{
Debug.Log(iValue);
};
}
// gc 136B
private void AnoymousFunctionWithLocalArg3()
{
int iValue = ;
int iValue2 = ;
actMember = () =>
{
Debug.Log(iValue);
Debug.Log(iValue2);
};
}
}
同时还可以发现，匿名函数引用的外部变量的个数会影响gc的值，为什么呢？来分析一波：
可以看到访问外部变量的匿名函数，会导致临时对象的创建，这样会导致gc，那位为什么每个临时变量的gc值不一样呢，我们来看一下这些临时class的定义：
可以看匿名函数所访问的外部变量都会在临时类里面创建一个拷贝，这样每个类对象的大小就不一样了。
附上类型定义的完整代码，前因后果一目了然：
public class TestAnonymousFunctionGC : MonoBehaviour
{
// Fields
private Action actMember;
private int iMember; // Methods
public TestAnonymousFunctionGC()
{
this.actMember = null;
this.iMember = ;
base..ctor();
return;
} [CompilerGenerated]
private void <AnoymousFunctionWithMemberArg>b__5_0()
{
Debug.Log((int) this.iMember);
return;
} private void AnoymousFunctionWithLocalArg1()
{
<>c__DisplayClass6_0 class_;
class_ = new <>c__DisplayClass6_0();
class_.bValue = ;
this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg1>b__0);
return;
} private void AnoymousFunctionWithLocalArg2()
{
<>c__DisplayClass7_0 class_;
class_ = new <>c__DisplayClass7_0();
class_.iValue = ;
this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg2>b__0);
return;
} private void AnoymousFunctionWithLocalArg3()
{
<>c__DisplayClass8_0 class_;
class_ = new <>c__DisplayClass8_0();
class_.iValue = ;
class_.iValue2 = ;
this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg3>b__0);
return;
} private void AnoymousFunctionWithMemberArg()
{
this.actMember = new Action(this.<AnoymousFunctionWithMemberArg>b__5_0);
return;
} private void AnoymousFunctionWithoutArg()
{
this.actMember = (<>c.<>9__4_0 != null) ? <>c.<>9__4_0 : (<>c.<>9__4_0 = new Action(this.<AnoymousFunctionWithoutArg>b__4_0));
return;
} private void Update()
{
Profiler.BeginSample("*** AnoymousFunctionWithoutArg ***");
this.AnoymousFunctionWithoutArg();
Profiler.EndSample();
Profiler.BeginSample("*** AnoymousFunctionWithMemberArg ***");
this.AnoymousFunctionWithMemberArg();
Profiler.EndSample();
Profiler.BeginSample("*** AnoymousFunctionWithLocalArg1 ***");
this.AnoymousFunctionWithLocalArg1();
Profiler.EndSample();
Profiler.BeginSample("*** AnoymousFunctionWithLocalArg2 ***");
this.AnoymousFunctionWithLocalArg2();
Profiler.EndSample();
Profiler.BeginSample("*** AnoymousFunctionWithLocalArg3 ***");
this.AnoymousFunctionWithLocalArg3();
Profiler.EndSample();
return;
} // Nested Types
[Serializable, CompilerGenerated]
private sealed class <>c
{
// Fields
public static readonly TestAnonymousFunctionGC.<>c <>;
public static Action <>9__4_0; // Methods
static <>c()
{
<> = new TestAnonymousFunctionGC.<>c();
return;
} public <>c()
{
base..ctor();
return;
} internal void <AnoymousFunctionWithoutArg>b__4_0()
{
return;
}
} [CompilerGenerated]
private sealed class <>c__DisplayClass6_0
{
// Fields
public bool bValue; // Methods
public <>c__DisplayClass6_0()
{
base..ctor();
return;
} internal void <AnoymousFunctionWithLocalArg1>b__0()
{
Debug.Log((bool) this.bValue);
return;
}
} [CompilerGenerated]
private sealed class <>c__DisplayClass7_0
{
// Fields
public int iValue; // Methods
public <>c__DisplayClass7_0()
{
base..ctor();
return;
} internal void <AnoymousFunctionWithLocalArg2>b__0()
{
Debug.Log((int) this.iValue);
return;
}
} [CompilerGenerated]
private sealed class <>c__DisplayClass8_0
{
// Fields
public int iValue;
public int iValue2; // Methods
public <>c__DisplayClass8_0()
{
base..ctor();
return;
} internal void <AnoymousFunctionWithLocalArg3>b__0()
{
Debug.Log((int) this.iValue);
Debug.Log((int) this.iValue2);
return;
}
}
} Collapse Methods
参考：https://blog.uwa4d.com/archives/Anonymous_heapmemory.html
Vector3.Equals函数会有gc:
// Vector3.Equeals有GC 28B
{
UnityEngine.Profiling.Profiler.BeginSample("*** Vector3.Equals ***");
Vector3 dir1 = Vector3.one, dir2 = Vector3.one;
var equals = dir1.Equals(dir2);
UnityEngine.Profiling.Profiler.EndSample();
}