Step 6 Nsoperation (Basic walkthrough)

• Nsoperation Abstract class
• Nsoperation is an "abstract class" and cannot be used directly
• The use of abstract classes is to define properties and methods common to subclasses
• In Apple's head file, some abstract classes and subclasses are defined in the same header file.
• Sub-class:

Nsinvocationoperation (Call)

Nsblockoperation (Block)

Nsoperationqueue queue

Basic Walkthrough

Nsinvocationoperation

Start

• The Start method executes the @selector method on the current thread

-(void) OpDemo1 {

Nsinvocationoperation *op = [[Nsinvocationoperation alloc] initwithtarget:self selector: @selector (downloadimage:) object:@ "Invocation"];

The Start method executes the @selector method on the current thread

[op start];

}

-(void) Downloadimage: (id) obj {

NSLog (@ "%@%@", [Nsthread CurrentThread], obj);

}

Add to queue

1 Adding an action to the queue will "asynchronously" execute the Selector method

-(void) OpDemo2 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

Nsinvocationoperation *op = [[Nsinvocationoperation alloc] initwithtarget:self selector: @selector (downloadimage:) object:@ "queue"];

[Q Addoperation:op];

}

Add multiple actions

-(void) OpDemo3 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

for (int i = 0; i < ++i) {

Nsinvocationoperation *op = [[Nsinvocationoperation alloc] initwithtarget:self selector: @selector (downloadimage:) object:@ (i)];

[Q Addoperation:op];

}

}

Execution effect: Multiple threads are turned on and not sequentially executed. Same as concurrent queue & asynchronous execution in GCD!

conclusion, in Nsoperation:

• Tasks performed asynchronously with operations
• Queues--Global queues

Nsblockoperation

-(void) OpDemo4 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

Nsblockoperation *op = [Nsblockoperation blockoperationwithblock:^{

NSLog (@ "%@", [Nsthread CurrentThread]);

}];

[Q Addoperation:op];

}

Using block to define the operation, all the code is written together, simpler and easier to maintain!

more simple, add directly Block

-(void) OpDemo5 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

for (int i = 0; i < ++i) {

[Q addoperationwithblock:^{

NSLog (@ "%@%d", [Nsthread CurrentThread], i);

}];

}

}

Add a different action to the queue

-(void) OpDemo5 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

for (int i = 0; i < ++i) {

[Q addoperationwithblock:^{

NSLog (@ "%@%d", [Nsthread CurrentThread], i);

}];

}

Nsblockoperation *OP1 = [Nsblockoperation blockoperationwithblock:^{

NSLog (@ "Block%@", [Nsthread CurrentThread]);

}];

[Q ADDOPERATION:OP1];

Nsinvocationoperation *OP2 = [[Nsinvocationoperation alloc] initwithtarget:self selector: @selector (downloadimage:) object:@ "Invocation"];

[Q ADDOPERATION:OP2];

}

• You can add subclasses of any nsoperation to Nsoperationqueue

Inter-thread communication

-(void) OpDemo6 {

Nsoperationqueue *q = [[Nsoperationqueue alloc] init];

[Q addoperationwithblock:^{

NSLog (@ "time-consuming Operation%@", [Nsthread CurrentThread]);

Main thread Update UI

[[Nsoperationqueue Mainqueue] addoperationwithblock:^{

NSLog (@ "Update UI%@", [Nsthread CurrentThread]);

}];

}];

}

Step 6 Nsoperation (Basic walkthrough)