Objective-C first day of study (BASICS)

Objective-c:

 

 

 

2.1.1-2.1.3 description

1. judging whether the memory of a variable is allocated to the stack gipo is a key method on the stack is to see if it is a pointer. A pointer is a variable pointing to a memory address.

 

 

2.1.4 use special variable modifiers.

Static keywords are considered as storage modifiers.

Const is similar to final in java

 

2.1.5 struct

Struct is represented by struct. To declare a struct, you must first tell the compiler struct itself, and then use this struct to declare a struct variable of the type already defined. The advantage of using struct is that it is a lightweight Method for storing variable groups, and struct has no overhead except for creating member variables that constitute it. Therefore, struct is sensitive to performance, not applicable to objects.

 

Struct can also contain struct, which is called composite struct.

 

2.1.6 type definition.

The type definition I understand is defined using typedef, and then we do not need to repeatedly define the structure we need to elaborate. You can use the type definition and struct together to better define a custom type to represent your struct .. Key Syntax: The typedef variable defines the new type name. Important

 

2.1.7 use enum

In java, the actual value of enumeration is determined by the compiler, but it is an integer by default. The first value is 0, the second value is 1, and so on.

You can use the type definition enumeration to avoid declaring enmu every time.

 

2.1.8 pointer:

A pointer is a variable that contains the address of another variable. The pointer operator is a (*). You can use the address operator (&) to obtain the address of a variable ,(*) the asterisk operator is also a pointer value operator. After the pointer value, you can access the value that the Pointer Points. In obj-c, you can regard an object as a pointer. At any time, you declare any object as a pointer.

 

2.1.9 use operators:

The related operation rules are the same as those in java.

 

2.1.10 three-object OPERATOR:

Same as java ,? :, Used to replace if/else