Use multiple threads of the iphone to implement the "ticket sales system" (hands-on Guide to iphone development-basics)

Author: Sun Dongfeng)

 

Java provides a lot of convenience for programmers because it supports multiple threads. In fact, it also supports multi-thread programming in iphone development, and it is no more troublesome than java.

In this article, I will take the classic "multi-thread Ticket System" in most Java tutorials as an example to implement the same in the iphone.

 

The following is the java version of the "multi-thread Ticket System" code:

Package demo;

Public class SellTickets implements Runnable {

Private int tickets = 100;

Public void run (){

Int count = 0;

While (true)

{

// Lock

Synchronized (this ){

If (tickets> 0 ){

Try {

Thread. sleep (500 );

} Catch (InterruptedException e ){

E. printStackTrace ();

}

Count = 100-tickets;

System. out. println ("the current number of votes is:" + tickets + "sold" + count

+ "Thread name:" + Thread. currentThread (). getName ());

Tickets --;

} Else {

Break;

}

}

}

}

Public static void main (String [] args ){

SellTickets r = new SellTickets ();

Thread t1 = new Thread (r, "t1 ");

T1.start ();

Thread t2 = new Thread (r, "t2 ");

T2.start ();

Thread t3 = new Thread (r, "t3 ");

T3.start ();

Thread t4 = new Thread (r, "t4 ");

T4.start ();

}

}

 

After the code of the above java version is executed, the console output is as follows:

Current ticket count: 100 sold 0 thread name: t1

Current ticket count: 99 sold 1 thread name: t2

Current ticket count: 98 sold 2 thread name: t3

Current ticket count: 97 sold 3 thread names: t4

Current ticket count: 96 sold 4 thread names: t1

Current ticket count: 95 sold 5 thread names: t2

Current ticket count: 94 sold 6 thread names: t3

Current ticket count: 93 sold 7 thread names: t4

Current ticket count: 92 sold 8 thread names: t1

Current ticket count: 91 sold 9 thread name: t2

Current ticket count: 90 sold 10 thread names: t3

Current ticket count: 89 sold 11 thread name: t4

Current number of votes: 88 sold 12 thread name: t1

Current ticket count: 87 sold 13 thread names: t2

Current ticket count: 86 sold 14 thread name: t3

Current number of votes: 85 sold 15 thread names: t4

Current ticket count: 84 sold 16 thread names: t1

Current ticket count: 83 sold 17 thread name: t2

Current ticket count: 82 Sold 18 thread names: t3

Current ticket count: 81 sold 19 thread names: t4

Current ticket count: 80 sold 20 thread names: t1

Current ticket count: 79 sold 21 thread name: t2

Current ticket count: 78 sold 22 thread name: t3

Current ticket count: 77 sold 23 thread name: t4

Current number of votes: 76 sold 24 thread name: t1

Current ticket count: 75 sold 25 thread name: t2

Current ticket count: 74 sold 26 thread names: t3

Current ticket count: 73 sold 27 thread names: t4

......

 

The same implementation can be performed on the iphone. The Iphone's Frameworks/Foundation. framework supports multi-threaded programming. The interface is defined in:

/Xcode3.1.4/Platforms/iPhoneSimulator. platform/Developer/SDKs/iPhoneSimulator3.1.sdk/System/Library

/Frameworks/Foundation. framework/Headers/NSThread. h

Open this file in the corresponding directory, and you can see that the vast majority of java interfaces can also find the corresponding implementation here, as shown below:

 

/* NSThread. h

Copyright (c) 1994-2007, Apple Inc. All rights reserved.

*/

 

# Import <Foundation/NSObject. h>

# Import <Foundation/NSDate. h>

 

@ Class NSArray, NSMutableDictionary, NSDate;

 

@ Interface NSThread: NSObject {

@ Private

Id_private;

Uint8_t _ bytes [44];

}

 

+ (NSThread *) currentThread;

 

+ (Void) detachNewThreadSelector :( SEL) selector toTarget :( id) target withObject :( id) argument;

 

+ (BOOL) isMultiThreaded;

 

-(NSMutableDictionary *) threadDictionary;

 

+ (Void) sleepUntilDate :( NSDate *) date;

+ (Void) sleepForTimeInterval :( NSTimeInterval) ti;

 

+ (Void) exit;

 

# If MAC_ OS _X_VERSION_10_2 <= MAC_ OS _X_VERSION_MAX_ALLOWED

+ (Double) threadPriority;

+ (BOOL) setThreadPriority :( double) p;

# Endif

 

# If MAC_ OS _X_VERSION_10_5 <= MAC_ OS _X_VERSION_MAX_ALLOWED

 

+ (NSArray *) callStackReturnAddresses;

 

-(Void) setName :( NSString *) n;

-(NSString *) name;

 

-(NSUInteger) stackSize;

-(Void) setStackSize :( NSUInteger) s;

 

-(BOOL) isMainThread;

+ (BOOL) isMainThread; // reports whether current thread is main

+ (NSThread *) mainThread;

 

-(Id) init; // designated initializer

-(Id) initWithTarget :( id) target selector :( SEL) selector object :( id) argument;

 

-(BOOL) isExecuting;

-(BOOL) isFinished;

 

-(BOOL) isCancelled;

-(Void) cancel;

 

-(Void) start;

 

-(Void) main; // thread body method

 

# Endif