Add msg_super usage note.

README.md

@@ -127,6 +127,7 @@ constructs by comparing the equivalent Objective-C and OCaml code.
 
 * Defining a new Cocoa class
 
+ Objective-C:
  ```objective-c
  @interface MyClass : NSObject {
  id myVar;
@@ -154,7 +155,10 @@ constructs by comparing the equivalent Objective-C and OCaml code.
  ]
  ```
 
- **_NOTE:_** If your method does not accept arguments, the `~args` parameter
+ **_NOTE:_**
+ The `~args` parameter includes only the explicit argument types.
+ The number of arguments is the same as the number of `:` in the selector.
+ If your method does not accept arguments, the `~args` parameter
  looks like this: `Objc_t.[]`
 
 * Memory management
@@ -184,6 +188,30 @@ constructs by comparing the equivalent Objective-C and OCaml code.
  an_instance |> msg_send (selector "anArbitrarySelector") ~args: Objc_t.[] ~return: Objc_t.void
  ```
 
+* Sending a message to the superclass
+
+ Eg, `viewDidLoad`:
+
+ Objective-C:
+ ```objective-c
+ - (void)viewDidLoad {
+ [super viewDidLoad]
+ ...
+ }
+ ```
+
+ OCaml:
+ ```OCaml
+ let viewDidLoad self cmd =
+ self |> msg_super cmd ~args: Objc_t.[] ~return: Objc_t.void;
+ ...
+ ```
+
+ **_NOTE:_**
+ Method implementations in OCaml always include two implicit parameters:
+ self - a pointer to the object;
+ cmd - the current selector
+
 ## Documentation
 
 At this time, the documentation of the project is lacking. The framework