Learn Objectvie-c on the MAC 2nd Edition notes

Chapter 1
Apple's Cocoa (for OS X) and Cocoa Touch (for IOS) toolkits are written in objective-c.

Chapter 2

(1). M stands for "messages" abbreviation

  C compiler  -C + + compiler, M-object-C compiler  

(2) in Objective-c, #import guarantees that each header file is included only once, as the #ifdef header file defender in C does.

(3) NSLog () is like printf () in C, but adds time and date stamps and automatically adds "\ n" newline characters at the end of the line.

@ ("") means that the string in "" is treated as a nsstring unit. If the C-style string "" is used directly in NSLog and the @ () is missing, a warning is obtained at compile time and the runtime is crash.

(4) Type BOOL

In Objectvie-c, the bool type is a typedef that is actually a signed char, so not only can you use Yes (value =1) and no (value =0) to represent true and false in C, but other values can be stored. Here's a simple mistake: If you assign a value of type such as short or int to a bool variable, the end of the 8 bits is truncated, and if the 8-bit value at the end is exactly 0 (for example, 8960, its hexadecimal value is 0x2300), the bool value of this value is 0, which is no, not No.

Chapter 3

(1) Core idea of computer science: indirection. Instead of using a value dirctly in your code, use a pointer to the value; Instead of doing something by yourself, ask another person to do it.

(2) A file read example:

#import<Foundation/Foundation.h>intMainintargcConst Char*argv[]) {    if(ARGC = =1) {NSLog (@"You need to provide a file Name"); return(1). } FILE*wordfile = fopen (Argv[1],"R"); ARGV[0] is the code file pathCharword[ -];  while(Fgets (Word, -, Wordfile) {         //strip off the trailing \ nWord[strlen (Word)-1] =' /'; NSLog (@"%s Kis%lu characters long", Word, strlen (word));    } fclose (Wordfile); return(0).} //Main

(3) in Objective-c, the method call uses infix notation (infix notation), such as

[Circle Setfillcolor:kredcolor];

If a method has no arguments, there is no colon and argument list, and if there are arguments, there is a colon:

-(void/ / no parameter -(void//  parameter )

Chapter 6

(1) The Code of the Objective-c class can be divided into 2 parts:

1>. @interface section

@interface xx:yy{    variables;} Public method declarations. @end

Provides a public interface declaration for this class.

2>. @implementation section

@implementation XX private self-used methods@end

Provides an implementation of this class and an intrinsic function.

Learn Objectvie-c on the MAC 2nd Edition notes