Preprocessor

Forms that compile (4)

Syntax	Description	Note
#nullable enable	Enabling null safety
#if FLAG / #else / #endif	Conditional compilation
#if UNITY_EDITOR	Editor-only code	It isn’t defined on the path this example was compiled through, so what it encloses wasn’t compiled.
#region / #endregion	Folding with #region	The compiled result doesn’t change.

Predefined symbols	Decided by whatever compiles the source. Including UNITY_EDITOR, they aren’t fixed to one set

Directives

Enabling null safety

From the line you write it on, the null-safety checks are enabled (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);   // => 1
#else
        Debug.Log(2);
#endif
    }
}

Editor-only code

UNITY_EDITOR is a symbol for the Unity editor.

using UnityEngine;
using Tsukimi;

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

Folding with #region

It becomes foldable in a code editor.

using UnityEngine;
using Tsukimi;

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