remove mention of old fields, add more stuff

Author: matcool

tutorials/fields.md

@@ -36,9 +36,9 @@ class $modify(PlayerObject) {
 
 This code works even if you have multiple `PlayerObject`s, and the counter is initialized as 0 for each one, providing an elegant yet simple solution to the problem.
 
-> :warning: If you are using old fields behavior, then **fields must be accessed through the `m_fields` member**. If you access them directly through `this`, you will get **undefined behaviour** (most likely a crash).
+Fields are declared just like normal member variables, but inside the special `Fields` struct. Even constructors and destructors work\*. 
 
-Fields are declared just like normal member variables, even constructors and destructors work\*. 
+> :info: Fields are initialized only whenever they're first accessed, **not** when the modified class is originally created.
 
 ```cpp
 class $modify(PlayerObject) {
@@ -60,7 +60,20 @@ class $modify(PlayerObject) {
 };
 ```
 
-## Note about addresses
+# External Access
 
-> :warning: If you are still using the old fields (which do not use the `Fields` struct), those ones are constructed and destructed in a different address than they exist normally (required for space optimization), so **if you have a class that depends on the address of `this` inside the constructor/destructor**, use `std::unique_ptr` to contain the said object. One such example would be Geode's events, since they are registered to a global map in their constructor.
+Fields can be accessed outside your modified class like usual, with the help of some casting.
 
+> :warning: Do not use `typeinfo_cast` here, as it isn't actually an instance of `MyGameObject`. 
+
+```cpp
+class $modify(MyGameObject, GameObject) {
+    struct Fields {
+        int m_myField = 2;
+    };
+};
+
+GameObject* someObject = /*...*/;
+// `m_fields` is still required!
+static_cast<MyGameObject*>(someObject)->m_fields->m_myField = 12;
+```