objective c(lang)

Objective CPart 1 Language

Overview

NeXTSTEP

Smalltalk

https://www.youtube.com/watch?v=j02b8Fuz73A

Language Design

Static and Strongly Typed

Keyword

No GC (ARC)

Superset of C (works as C compiler)

Not method but message

Protocol & Delegate Category

Hello World

NSLog(@“Hello World”);

Interpolation %@

Types

C types

int, char, float, const, unsigned

Objective C

NSObject, NSString, NSNumber, NSArray, NSDictionary

NSMutableArray

id

Methods [Messages]

obj.method(param);

[objmessage:param];

[objsayHello:@“Hello!”];

Methods [Messages]

obj.method(param1, param2);

[obj message:param1, keyword2:param2]

[person setFirst:@“John” setLast:@“Doe” setAge:@34]

The message signature is setFirst:setLast:setAge:

- (void) sayHello: (NSString *) param {

NSLog(@“Hello %@ World”, param);

};

- (String) sayHello:(Type)param1

keyword2:(Type)param2

keyword3:(Type)param3 {};

Methods [Messages]@Implementation

List and Dictionary

NSArray*list=@[obj1,obj2,obj3,…];

NSDictionary*dict=@{key:val,key:val}NSDictionary*dict=@{key:val,key:val}

^Callback (Block)

^ refers to an anonymous function

Define a block called Callback, which takes a NSString, then return void

Pass in a block

Implement a method called ajax:word:ajax takes a Callback type

ClassPerson.h

Person.m

Caller.m

#import “Person.h”

Person *p = [Person new];

@interface

@end

@implementation

@end

- (void) sayHello {…};

- (void) sayHello;

[p sayHello];

visible

implement

Class

Person.h

Person.m

Caller.m

Selector

Reflection in Java

SEL method = NSSelectorFromString(@“getFullname”);

[obj performSelector:method];

<Protocol>Interface in Java

C21Protocol.h

Delegate Pattern

Like Java, Protocol is used in Delegate Pattern. But, use of Block is recommended.

-doYouKnowObjectiveC

<Protocol>

Developer.m

Manager.mClient

Delegate patterns are used in Views and Controllers. I’ll show you the code in the GUI part.

- delegate

-doYouKnowObjectiveC

Category

Extends the existing class (like Ruby’s monkey patch)

Person+age.h

Person+age.mCaller.m

To extend Person, prepare two files called:

Person+age.hPerson+age.m

Add getAge()

Class Extension

Class extension is like anonymous Category ()

Define @interface in a .m file

The methods are private scope.

They are not visible from outside of the file.

Property Option (avoid memory leak)

Button

View Controller

(weak) btnStrongweak

View points to the Button object strongly,

while Controller.btn points to the Button weekly.

Thus, Compiler (ARC) can delete the Button object when the Strong link is detached.There is no GC in Objective-C. Compiler will insert destructor statements.