Embedded & amp; iOS: callback function (C) and block (OC) callback comparison, embedded training

Embedded & iOS: callback function (C) and block (OC) callback comparison, embedded training

After learning the OC block, it is awkward to write the C callback function. Compare the difference and record it.

 

C callback function:

CallBack. h

1) define the number and type of parameters for a callback function.

typedef void (*CallBack)(int data_i32);

2) declare an external function pointer.

extern CallBack myCallBackPTR;

3) declare a doSomeThingCount Function

void DSTCount(void);

 

CallBack. c

1) define a function pointer

CallBack myCallBackPTR;

2. In the doSomeThingCount function, increase the number of running times and call the function pointer.

void DSTCount(void){    static int numb = 0;    numb++;    (*myCallBackPTR)(numb);}

 

Main. c

1) define a customdoSomeThingCount function to print data

void customDSTCount(int data_i32){    printf("%d\n",data_i32);}

2) in the main function, point the callBack. h function pointer to main mdstcount of main and run the DSTCount function of callBack. h.

myCallBackPTR = customDSTCount;    while (1){    DSTCount();}

 

Advantages: 1. You can modify and supplement the callBack file through main or other files without modifying the callBack file.

Purpose: 1. For example, a temperature sensor peripheral. c ,. h has been written. If you don't want others to modify it, set it to read-only. By setting the callback function pointer, you can set the filtering method, or weight filtering, or average value filtering as needed.

Supplement: 1. the callback function in UCOS is like a hook (hooks) function. Is it completely equivalent? I will add it later.

 

 

 

OC Block:

MyButton. h (inherited from UIButton ):

1) define the number and type of parameters of a Block. (Basically similar, c is *, oc is ^)

typedef void(^ButtonBlock)(int data_i32);

2) declare and define a Block variable. (Similar)

@property (nonatomic,strong) ButtonBlock myButtonBlockPTR;

3) declare a doSomeThingCount function. (Similar)

-(void)DSTCount;

 

MyButton. m (inherited from UIButton ):

1) In the doSomeThingCount function, increase the number of running times and call the Block variable. (Basically similar, C is (* xx) (yy), OC is xx (yy ))

-(void)DSTCount{    static int numb = 0;    numb++;    _myButtonBlockPTR(numb);}

 

RootViewControl. m (self. window. rootViewController ):

1) viewDidLoad function, defines a (100,100,100,100), red button instance, write in the Block of the button, print times, button add event, Add button to self. view

MyButton *tempButton = [[MyButton alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];    tempButton.backgroundColor = [UIColor redColor];    tempButton.myButtonBlockPTR = ^(int data_i32){    printf("%d\n",data_i32);};[tempButton addTarget:self action:@selector(mybuttonClick:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:tempButton];

2. click the button to call the DSTCount function in MyButton.

-(void)mybuttonClick:(MyButton*)button{    [button DSTCount];}

 

Comparison: Block implementation is written in parentheses when setting variables, rather than pointing to functions.

The callback function of C is just a pointer and must point to the function.

Supplement: Compared with the callback function of C, Block is more useful.

 

 

 

 

 

Image supplement:

C callback function:

1) CallBack. C

2) CallBack. h

3). main. c

 

 

 

OC Block

1) MyButton. h

2) MyButton. m

3) RootViewControl. m

4) Run