Chapter 14 — More Messages
- As we saw before, Objective-C methods can have multiple parameters.
Nesting message sends
- We saw this in chapter 12 with no explanation.
- Does that look a little strange? It is sending messages that are nested and is very common in Objective-C.
- Here’s what it’s doing. First, get some memory that holds an NSDateComponents object with the
- Then send the
init message to the object to initialize and configure the object.
- However, it is more concise and a full convention to do it this way.
Two ways to make an
- First, with a class method
- Now with the
alloc class method and the
init instance method.
- These two ways are fully equivalent.
Sending messages to
- This is a nice feature of Objective-C! You can send a message to
nil and it doesn’t fail and it doesn’t create error messages.
- The keyword
nil is the Objective-C version of
NULL in C.
- In Objective-C you can do this.
- The special keyword
id is “a pointer to some kind of Objective-C object.”
- A pointer to a specific class:
- A pointer to a class where we don’t what the class is.