iOS Development Multithreading Basics Nsoperation

-------nsoperation Introduction----The role of 1.NSOperation • With the use of nsoperation and nsoperationqueue can also achieve multi-threaded programming 2.NSOperation and nsoperationqueue multi-threaded implementation of the specific steps · Wrap the action you need to perform into a Nsoperation object • Then add the Nsoperation object to the Nsoperationqueue • The system automatically places the actions encapsulated in the nsoperation in a new threadSubclass of---------nsoperation----3.NSOperation is an abstract class and does not have the ability to encapsulate operations, it must use its subclass 4. There are 3 ways to use the Nsoperation subclass · Nsinvocationoperation Nsblockoperation Custom Subclass Inherits Nsoperation, implements the internal corresponding method------nsinvocationoperation---5. Create a Nsinvocationoperation object

-(ID) Initwithtarget: (ID) Target selector: (SEL) Sel object: (ID) arg;

6. Call the Start method to start the operation

-(void) start;

Once the operation is performed, the Sel method of the target is called

7. Note • By default, when the Start method is called, it does not open a new thread to perform the operation, but instead performs the operation synchronously on the current thread • Operations are performed asynchronously only if the nsoperation is placed in a nsoperationqueue-------nsblockoperation--8. Create a Nsblockoperation object

+ (ID) Blockoperationwithblock: (void (^) (void)) block;

9. Add more actions by Addexecutionblock: method

-(void) Addexecutionblock: (void (^) (void)) block;

Note: The operation is performed asynchronously as long as the nsblockoperation encapsulated operand > 1

-------Nsoperationqueue----

The role of 10.NSOperationQueue · Nsoperation can invoke the Start method to perform a task, but it is performed synchronously by default • If you add nsoperation to the Nsoperationqueue (action queue), the system automatically executes operation 11 in Nsoperation. Adding actions to Nsoperationqueue

-(void) Addoperation: (Nsoperation *) op;

-(void) Addoperationwithblock: (void (^) (void)) block;

-------Maximum number of concurrent----

12. What is concurrency • Number of simultaneous tasks • For example, 3 threads are executing 3 tasks simultaneously, and the concurrency count is 3 13. Correlation method of maximum concurrency number

-(Nsinteger) Maxconcurrentoperationcount;

-(void) Setmaxconcurrentoperationcount: (Nsinteger) CNT;

-----The cancellation, pause, resume------of a queue

14. Cancel all operations on a queue

-(void) cancelalloperations;

Tip: You can also call the Nsoperation-(void) Cancel method to cancel a single operation

15. Pausing and resuming queues

-(void) setsuspended: (BOOL) b; Yes means pause queue, no for recovery queue

-(BOOL) issuspended;

----Operation Priority-----

16. Set the priority of the nsoperation in the queue to change the order in which the operations are executed

-(nsoperationqueuepriority) queuepriority;

-(void) Setqueuepriority: (nsoperationqueuepriority) p;

17. The priority value (the higher the priority, the more the first execution) · Nsoperationqueuepriorityverylow = -8l, Nsoperationqueueprioritylow = -4l, Nsoperationqueueprioritynormal = 0, Nsoperationqueuepriorityhigh = 4, Nsoperationqueuepriorityveryhigh = 8---operation dependent---A dependency can be set between 18.NSOperation to guarantee the order of execution • For example, make sure that operation A is done before you can perform operation B, so write

[Operationb Adddependency:operationa]; Action B depends on action a

19. You can create a dependency between nsoperation of different queue

Note: cannot depend on each other

• For example a relies on b,b dependency a----The execution order of the operation---21. For operations added to the queue, the order in which they are executed depends on 2 points • First depending on the dependency between nsoperation • Then according to the priority of the Nsoperation 22. Therefore, the overall order of execution is first to satisfy the dependencies · Then choose the highest-priority execution from the nsoperation.---custom nsoperation---23. The steps to customize the nsoperation are simple • Rewrite-(void) The Main method, where you implement the task that you want to perform 24. overriding-(void) The note point of the Main method • Create an auto-free pool yourself (because if it is an asynchronous operation, you cannot access the auto-free pool of the main thread) · Often pass-(BOOL) IsCancelled method detects whether the operation is canceled, responds to cancellation--------Split line---nsoperation small code 1, write only one file reference

dyfviewcontroller.m//624-03-nsoperation////Created by dyf on 14-6-24.//Copyright (c) 2014 ___fullusername___. All rights reserved.//#import "DYFViewController.h" @interface Dyfviewcontroller () @end @implementation dyfviewcontroller-(void) viewdidload{[Super viewdidload];//do any additional setup after loading the view, typically          From a nib. [Self testoperationqueue];} -(void) Testoperationlisten {nsblockoperation *operation3 = [nsblockoperation blockoperationwithblock:^{NSLog (        @ "Download picture 1111111%@", [Nsthread CurrentThread]);    Download picture}];    Operation3.completionblock = ^{//Download the picture after the time you want to do};    2. Create queue Nsoperationqueue *queue = [[Nsoperationqueue alloc] init]; [Queue Addoperation:operation3];} -(void) Testoperationqueue {//1. Encapsulation operation nsinvocationoperation *operation1 = [[Nsinvocationoperation alloc] Initwithta    Rget:self selector: @selector (download) Object:nil]; Nsinvocationoperation *operation2 = [[Nsinvocationoperation alloc]Initwithtarget:self selector: @selector (run) Object:nil]; Nsblockoperation *operation3 = [nsblockoperation blockoperationwithblock:^{NSLog (@ "1111111%@", [NSThread currentTh    Read]);        }];    [Operation3 addexecutionblock:^{NSLog (@ "222222%@", [Nsthread CurrentThread]);    }];    [Operation3 addexecutionblock:^{NSLog (@ "33333%@", [Nsthread CurrentThread]);    }];    2. Create queue Nsoperationqueue *queue = [[Nsoperationqueue alloc] init]; Within 5, the appropriate queue.maxconcurrentoperationcount = 2; #warning face question//set operation dependencies (be sure to set before adding to the queue) [Operation2 Adddependenc Y:operation1]; The order of execution depends on the dependency, first executing the operation1 and then executing operation2//Note: Cannot depend on each other, loop operation//3. Add an action to the queue (auto-execute, auto-open thread) [Queue Addoperation:opera    Tion1];    [Queue Addoperation:operation2];        [Queue Addoperation:operation3];        Cancel all threads//[queue Cancelalloperations];        Pause queue//[queue Setsuspended:yes];       Set operation priority//operation1.queuepriority = Nsoperationqueuepriorityveryhigh; }-(void) Testnsblockoperation {//1. Create an Action object that encapsulates the task to be performed nsblockoperation *operation = [Nsblockoperation blockoperation        withblock:^{for (int i = 0; i <; i++) {NSLog (@ "1111111%@", [Nsthread CurrentThread]);    }    }]; The number of tasks above 2, will be the thread [Operation addexecutionblock:^{for (int i = 0; i < one; i++) {NSLog (@ "222222%@")        , [Nsthread CurrentThread]);    }    }]; [Operation addexecutionblock:^{for (int i = 0; i <; i++) {NSLog (@ "33333%@", [Nsthread currentthr        EAD]);    }    }]; 2. Perform the operation [operation start];} -(void) Testnsinvocationoperation {//1. Create an Action object that encapsulates the task to be performed nsinvocationoperation *operation = [[Nsinvocationoperation    Alloc] initwithtarget:self selector: @selector (download) Object:nil]; 2. Perform the operation (by default, if the operation is not placed in the queue, it will be performed synchronously) [Operation start];}    -(void) download{for (int i = 0; i <; i++) {NSLog (@ "Download-----%@", [Nsthread CurrentThread]); }}-(void) run{for (int i = 0; I < 11;    i++) {NSLog (@ "Run------%@", [Nsthread CurrentThread]); }} @end

----Custom Nsoperation---

  dyfdownloadoperation.h//  624-05-Custom operation////  Created by dyf on 14-6-24.//  Copyright (c) 2014 DYF. All rights reserved.//#import <Foundation/Foundation.h> @class dyfdownloadoperation; @protocol Dyfdownloadoperationdelegate <NSObject> @optional-(void) Downloadoperation: (dyfdownloadoperation *) operation Didfinisheddownload: (UIImage *) image; @end @interface dyfdownloadoperation:nsoperation@property (nonatomic, copy) NSString *url; @property (nonatomic, strong) Nsindexpath *indexpath; @property (nonatomic, weak) id< Dyfdownloadoperationdelegate> delegate; @end

  dyfdownloadoperation.m//  624-05-Custom operation////  Created by dyf on 14-6-24.//  Copyright (c) 2014 DYF. All rights reserved.//#import "DYFDownloadOperation.h" @implementation dyfdownloadoperation/** *  to implement specific actions in the Main method * /-(void) main{    @autoreleasepool {        if (self.iscancelled) return;        Nsurl *imaurl = [Nsurl URLWithString:self.url];        if (self.iscancelled) return;        The following line is time consuming        nsdata *data = [NSData Datawithcontentsofurl:imaurl];        if (self.iscancelled) return;        UIImage *image = [UIImage imagewithdata:data];        if (self.iscancelled) return;                Returns the main thread display picture        //via proxy        if ([Self.delegate respondstoselector: @selector (downloadoperation: Didfinisheddownload:)] {            [self.delegate downloadoperation:self didfinisheddownload:image];}        }    @end

Use the MVC pattern to create a file of the old cliché, only a controller.m file for reference, data storage problems, you can use the Sdwebimage framework to handle

dyftableviewcontroller.m//624-05-Custom operation////Created by dyf on 14-6-24.//Copyright (c) 2014 ___fulluserna me___. All rights reserved.//#import "DYFTableViewController.h" #import "DYFAppModel.h" #import "DYFDownloadOperation.h" # Warning Dictionary basic knowledge not very understanding, dictionary assignment go back to see notes @interface Dyftableviewcontroller () <dyfdownloadoperationdelegate>@ Property (Nonatomic, Strong) Nsarray *apps; @property (nonatomic, strong) nsoperationqueue *queue;/** * Key:url value:op Eration Object */@property (nonatomic, strong) nsmutabledictionary *oprations;/** * Key:url value:image Object */@property (Nonat Omic, strong) nsmutabledictionary *images; @end @implementation dyftableviewcontroller#pragma mark-4 Lazy Loading-(NSArray *)        apps{if (!_apps) {NSString *path = [[NSBundle Mainbundle] pathforresource:@ "apps" oftype:@ "plist"];                Nsarray *arrayapps = [Nsarray Arraywithcontentsoffile:path];        Nsmutablearray *arraym = [Nsmutablearray arrayWithCapacity:arrayApps.count]; for (NSDIctionary *dict in Arrayapps) {Dyfappmodel *appm = [Dyfappmodel appwithdict:dict];        [Arraym addobject:appm];    } _apps = Arraym; } return _apps;}        -(Nsoperationqueue *) queue{if (!_queue) {_queue = [[Nsoperationqueue alloc] init];    Set the maximum number of concurrent threads and download up to 3 images at the same time _queue.maxconcurrentoperationcount = 3; } return _queue;}    -(Nsmutabledictionary *) oprations{if (!_oprations) {_oprations = [[Nsmutabledictionary alloc] init]; } return _oprations;}    -(Nsmutabledictionary *) images{if (!_images) {_images = [nsmutabledictionary dictionary]; } return _images;} -(void) viewdidload{[Super viewdidload];//do no additional setup after loading the view, typically from a nib.} #pragma mark-Data source Method-(Nsinteger) TableView: (UITableView *) TableView numberofrowsinsection: (Nsinteger) section{return s Elf.apps.count;} -(UITableViewCell *) TableView: (UITableView *) TableView Cellforrowatindexpath: (NSINDEXPATH *) INDexpath{//1. Create cell static NSString *identifier = @ "apps";    UITableViewCell *cell = [TableView dequeuereusablecellwithidentifier:identifier]; if (!cell) {cell = [[UITableViewCell alloc] Initwithstyle:uitableviewcellstylesubtitle Reuseidentifier:identifier]    ;    }//2. Set the cell's data Dyfappmodel *app = Self.apps[indexpath.row];    Cell.textLabel.text = App.name;        Cell.detailTextLabel.text = App.download; The point is how to download images from the network into the cell above//each URL corresponds to a Dyfdownloadoperation object//Each URL corresponds to an image object UIImage *image = self.images[app.i    Con];    if (image) {//If a picture is present in the cache cell.imageView.image = image; }else {//If a picture is not present in the cache, the picture will be downloaded from the Web//set before the system is downloaded cell.imageView.image = [UIImage imagenamed:@ "ID small"]                ;        Base difference, the following line does not understand dyfdownloadoperation *operation = Self.oprations[app.icon]; if (operation) {//If you are downloading, do not perform other actions}else {//If not downloaded, create a child thread to start the download dyfdownload Operation *Operation = [[Dyfdownloadoperation alloc] init];            Operation.url = App.icon;            Operation.indexpath = Indexpath;            Operation.delegate = self;            Add task into queue, asynchronous download [Self.queue addoperation:operation];        The base is poor, the following line does not understand self.oprations[app.icon] = operation; }}//3. Return to cell return cell;} #pragma mark-dyfdownloadoperationdelegate-(void) Downloadoperation: (dyfdownloadoperation *) operation    Didfinisheddownload: (UIImage *) image{//1. Delete the completed download operation [Self.oprations RemoveObjectForKey:operation.url];        If the picture is downloaded good if (image) {///2. Save the downloaded picture in cache self.images[operation.url] = image; 3. Refresh the data for this row of cells [Self.tableview Reloadrowsatindexpaths:@[operation.indexpath] Withrowanimation:uitableviewrowani        Mationnone];        4. Save picture into Sandbox//4.1 picture first convert to 2 binary data nsdata *data = uiimagepngrepresentation (image); 4.2 Set sandbox path nsstring *path = [[NssearchpathfordirectoriesIndomains (NSDocumentDirectory, Nsuserdomainmask, YES) Lastobject] stringbyappendingpathcomponent:[self.apps[        Operation.indexPath.row] [icon]];        NSLog (@ "%@", Path);    4.3 Save data to path [data Writetofile:path Atomically:yes]; }}//start dragging when the queue is paused-(void) scrollviewwillbegindragging: (Uiscrollview *) scrollview{[Self.queue Setsuspended:yes];} Restart queue when dragging is stopped-(void) scrollviewwillenddragging: (Uiscrollview *) ScrollView withvelocity: (cgpoint) Velocity Targetcontentoffset: (inout cgpoint *) targetcontentoffset{[Self.queue setsuspended:no];} @end