1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
---
language: Objective-C
contributors:
- ["Eugene Yagrushkin", "www.about.me/yagrushkin"]
- ["Yannick Loriot", "https://github.com/YannickL"]
filename: LearnObjectiveC.m
---
Objective-C is the main programming language used by Apple for the OS X and iOS operating systems and their respective frameworks, Cocoa and Cocoa Touch.
It is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language.
```Objective-C
// Single-line comments start with //
/*
Multi-line comments look like this.
*/
// Imports the Foundation headers with #import
#import <Foundation/Foundation.h>
// Your program's entry point is a function called
// main with an integer return type.
int main (int argc, const char * argv[])
{
// Create an autorelease pool to manage the memory into your program
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// Use NSLog to print lines to the console
NSLog(@"Hello World!"); // Print the string "Hello World!"
// String object
NSString *worldString = @"World";
// %@ is an object
NSLog(@"Hello %@!", worldString); // Print "Hello World!"
// Character literals
NSNumber *theLetterZ = @'Z';
NSLog(@"%c", [theLetterZ charValue]);
// Integral literals
NSNumber *fortyTwoNumber = @42;
int fortyTwo = [fortyTwo intValue];
NSLog(@"%i", fortyTwo);
NSNumber *fortyTwoUnsignedNumber = @42U;
unsigned int fortyTwoUnsigned = [fortyTwoUnsigned unsignedIntValue];
NSLog(@"%u", fortyTwoUnsigned);
NSNumber *fortyTwoLongNumber = @42L;
long fortyTwoLong = [aLong longValue];
NSLog(@"%li", fortyTwoLong);
// Floating point literals
NSNumber *piFloatNumber = @3.141592654F;
float piFloat = [piFloat floatValue];
NSLog(@"%f", piFloat);
NSNumber *piDoubleNumber = @3.1415926535;
piDouble = [piDouble doubleValue];
NSLog(@"%f", piDouble);
// BOOL literals
NSNumber *yesNumber = @YES;
NSNumber *noNumber = @NO;
// Array object
NSArray *anArray = @[@1, @2, @3, @4];
NSNumber *thirdNumber = anArray[2];
NSLog(@"Third number = %@", thirdObject); // Print "Third number = 3"
// Dictionary object
NSDictionary *aDictionary = @{ @"key1" : @"value1", @"key2" : @"value2" };
NSObject *valueObject = aDictionary[@"A Key"];
NSLog(@"Object = %@", valueObject); // Print "Object = (null)"
// Clean up the memory you used into your program
[pool drain];
// End your program
return 0;
}
///////////////////////////////////////
// Classes And Functions
///////////////////////////////////////
// Declare your class in a header(.h) file:
@interface UserObject : NSObject
{
// instance variables
}
// Class method
+ (NSString *)classMethod;
// Instance method
- (NSString *)instanceMethodWithParmeter:(NSString *)string;
@end
// Implement the methods in an implementation (.m) file:
@implementation UserObject
+ (NSString *)classMethod
{
return @"SomeString";
}
- (NSString *)instanceMethodWithParmeter:(NSString *)string
{
return @"New string";
}
- (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number
{
return @42;
}
@end
// Create an object instance by allocating memory and initializing it. An object is not fully functional until both steps have been completed.
UserObject *someObject = [[UserObject alloc] init];
##Calling Methods
// The Objective-C model of object-oriented programming is based on message passing to object instances.
// In Objective-C one does not simply call a method; one sends a message.
[someObject instanceMethodWithParmeter:@"Steve Jobs"];
##Nested Messages
// nested messages look like this:
[someObject instanceMethodWithParmeter:[someObject otherMethodWithString:@"Jony Ive"]];
```
## Further Reading
[Wikipedia Objective-C](http://en.wikipedia.org/wiki/Objective-C)
[Learning Objective-C](http://developer.apple.com/library/ios/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/)
[iOS For High School Students: Getting Started](http://www.raywenderlich.com/5600/ios-for-high-school-students-getting-started)
|
