Preprocessor

Forms that compile (4)

Syntax	Description
#nullable enable	Enabling null safety
#if FLAG / #else / #endif	Conditional compilation
#if UNITY_EDITOR	Editor-only code
#region / #endregion	Foldable regions

Which symbols are defined depends on whoever compiles the source. Defined symbols, including UNITY_EDITOR, aren’t fixed to one set.

Directives

Enabling null safety

Null safety checks apply from the line you write it onward (Null and references).

#nullable enable
using UnityEngine;
using Tsukimi;

public class PreNullableEnable : TsukimiBehaviour
{
    void Start()
    {
        string s = "a";
        Debug.Log(s.Length);   // => 1
    }
}

Conditional compilation

#define FLAG
using UnityEngine;
using Tsukimi;

public class PreConditional : TsukimiBehaviour
{
    void Start()
    {
#if FLAG
        Debug.Log(1);
#else
        Debug.Log(2);
#endif
    }
}

// Output
// 1

Editor-only code

UNITY_EDITOR is a symbol for the Unity Editor. It isn’t defined on the path this example takes, so the enclosed code doesn’t compile.

using UnityEngine;
using Tsukimi;

public class PreEditorOnly : TsukimiBehaviour
{
    void Start()
    {
#if UNITY_EDITOR
        Debug.Log(1);
#endif
        Debug.Log(2);
    }
}

// Output
// 2

Foldable regions

It becomes a foldable region in the code editor. The compiled result doesn’t change.

using UnityEngine;
using Tsukimi;

public class PreRegion : TsukimiBehaviour
{
#region Body
    void Start()
    {
        Debug.Log(1);   // => 1
    }
#endregion
}