OBJECTIVE-C----First knowledge of objective-c

First knowledge of Objective-c

When Objective-c was first born, the extension. m stands for message, which refers to a major feature of Objective-c.

NSLog (@ “% d”, 12); // can output 12
printf ("% d \ n", 23); // can output 23
NSLog (@ "% s", "abc"); // Can output string abc
printf ("% s", "abc"); // print string abc 

The programming style of "data first, function second";

Following the open/closed programming principle, when encapsulating a class, we can extend it without modifying the internal implementation.

Bugs are nowhere to hide unless the code is streamlined.

OC does not allow initialization of member variables in the interface (interface).

The interaction between all objects in the objective-c is accomplished by pointers.

Example: (will report an error)

If you do file extensions with. mm, the compiler will think that you are writing code with objective-c++, so you can use both C + + and objective-c to program.

OBJECTIVE-C----First knowledge of objective-c