objectc 与 js 交互

Execute Javascript in iOS Applications

In this tutorial, I have covered How to execute JavaScript in iOS / Objective-C. You can execute JavaScript in iOS applications with the help of JavaScriptCore.framework. This framework is supported in iOS7 & OSX 10.9

List of features supported by Javascript.framework
a) Evaluate JavaScript code in Objective-C
b) Access JavaScript Variables in Objective-C
c) Access JavaScript functions and execute them in Objective-C
d) Execute Objective-C code from JavaScript
e) Export Objective-C classes and use them in JavaScript.

Download the source code: 

To access JavaScript framework, you need to include the header file

1	#import <JavaScriptCore/JavaScriptCore.h>

List of Main Classes supported by framework:
JSContext : For any javascript operations you need JSContext.

1	JSContext  *context = [[ JSContext  alloc ]  init ];

JSValue : JSValue holds JavaScript values,variables and functions. List of main methods in JSValue.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

// Convert this value to a corresponding Objective-C object, according to the // conversion specified above. - ( id )toObject;   // Convert this value to a corresponding Objective-C object, if the result is // not of the specified class then nil will be returned. - ( id )toObjectOfClass:(Class)expectedClass;   // The value is copied to a boolean according to the conversion specified by the // JavaScript language. - ( BOOL )toBool;   // The value is copied to a number according to the conversion specified by the // JavaScript language. - ( double )toDouble;   // The value is copied to an integer according to the conversion specified by // the JavaScript language. - (int 3 2 _t)toInt 3 2 ;   // The value is copied to an integer according to the conversion specified by // the JavaScript language. - (uint 3 2 _t)toUInt 3 2 ;   // If the value is a boolean, a NSNumber value of @YES or @NO will be returned. // For all other types the value will be copied to a number according to the // conversion specified by the JavaScript language. - ( NSNumber  *)toNumber;   // The value is copied to a string according to the conversion specified by the // JavaScript language. - ( NSString  *)toString;   // The value is converted to a number representing a time interval since 1970, // and a new NSDate instance is returned. - ( NSDate  *)toDate;   // If the value is null or undefined then nil is returned. // If the value is not an object then a JavaScript TypeError will be thrown. // The property "length" is read from the object, converted to an unsigned // integer, and an NSArray of this size is allocated. Properties corresponding // to indicies within the array bounds will be copied to the array, with // Objective-C objects converted to equivalent JSValues as specified. - ( NSArray  *)toArray;   // If the value is null or undefined then nil is returned. // If the value is not an object then a JavaScript TypeError will be thrown. // All enumerable properties of the object are copied to the dictionary, with // Objective-C objects converted to equivalent JSValues as specified. - ( NSDictionary  *)toDictionary;

 

Accessing Javascript Code in Objective-C

1).Evaluating Javascript Code

1 2 3 4

NSString  * jsCode = @"1+2" ; JSContext  *context = [[ JSContext  alloc ]  init ]; JSValue  * value = [context  evaluateScript :jsCode]; NSLog( @"Output = %d" , [value  toInt32 ]);

 

2).Access Javascript Variables. Variables and functions are accessed from JSContext.
To access varible from Javascript : context[@"x"]
To access function from javascript : context[@"myfun"]

1 2 3 4 5 6

JSContext  *context = [[ JSContext  alloc ]  init ];      NSString  * jsCode = @"var x; x=10;" ;      [context  evaluateScript :jsCode];        JSValue  * a =context[ @"x" ];      NSLog( @"x = %d" , [a  toInt32 ]);

 

3).Access Javascript functions and execute them in Objective-C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

//function with arguments      JSContext  *context = [[ JSContext  alloc ]  init ];      NSString  * jsCode = @"function sum(a,b) { return a+b;} " ;      [context  evaluateScript :jsCode];        JSValue  * func =context[ @"sum" ];      NSArray  * args = @[[ NSNumber  numberWithInt : 1 0 ],[ NSNumber  numberWithInt : 2 0 ]];      JSValue  * ret =[func  callWithArguments :args];      NSLog( @"10+20 = %d" , [ret  toInt32 ]);        //function without arguments      NSString  * jsCode 2  = @"function getRandom() { return parseInt(Math.floor((Math.random()*100)+1));} " ;      [context  evaluateScript :jsCode 2 ];        JSValue  * func 2  =context[ @"getRandom" ];        for ( int  i= 0 ;i< 5 ;i++)      {          JSValue  * ret 2  =[func 2  callWithArguments :nil ];          NSLog( @"Random Value = %d" , [ret 2  toInt32 ]);      }

 

Call Objective-C code from JavaScript

Objective-C code is called from JavaScript in two ways

1.CODE BLOCKS

Objective-C code block can be called from JavaScript.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

JSContext  *context = [[ JSContext  alloc ]  init ];        //we are telling that "sum" is function, takes two arguments      context[ @"sum" ] = ^( int  arg 1 , int  arg 2 )      {          return  arg 1 +arg 2 ;      };        NSString  * jsCode = @"sum(4,5);" ;      JSValue  * sumVal = [context  evaluateScript :jsCode];        NSLog( @"Sum(4,5) = %d" , [sumVal  toInt32 ]);        //we are telling that "getRandom" is function, does not take any arguments      context[ @"getRandom" ] = ^()      {          return  rand()% 1 0 0 ;      };        NSString  * jsCode 2  = @"getRandom();" ;      for ( int  i= 0 ;i< 5 ;i++)      {          JSValue  * sumVal 2  = [context  evaluateScript :jsCode 2 ];          NSLog( @"Random Number = %d" , [sumVal 2  toInt32 ]);      }

 

2.USING JSEXPORT PROTOCOL

You can see the comparison between Objective-C Object and it’s equivalent Javascript Object below.

1 2 3 4 5 6 7 8 9 10 11 12 @interface  MyObject @property   int  x;   -( int ) getX; +( MyObject  *)  getSqure :(MyObject*)obj;   @end   //Usage: MyObject  * obj = [ MyObject  new ]; [obj  getX ]; [ MyObject  getSqure :obj];

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 function  MyObject() {      //member variable      this .x=0;        //instance method      this .getX = function ()                      {                      return  this .x;                      } }   //static method MyObject.getSqure = function (obj) {      var  newObj = new  MyObject();      newObj.x = obj.x * obj.x;      return  newObj; }   //Usage: var  obj = new  MyObject(); obj.x=10; var  sqrObj = MyObject.getSqure(obj);

To make Javascript interacting with Objective-C Object, We need to have a Protocol which should be inherited
from JSExport. Move all the variables and functions to prototype to access them in JavaScript.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

@protocol  MyObjectExport @property   int  x;   -( int ) getX; +( MyObject  *)  getSqure :(MyObject*)obj;   @end   @interface  MyObject  : NSObject  <MyObjectExport>   //this method is not accessible in javascript -( void ) test;   @end ;   @implementation  MyObject @synthesize  x;   -( int ) getX {      return  self .x ; } +( MyObject  *)  getSqure :(MyObject*)obj; {      NSLog( @"Calling getSqure" );      MyObject  * newObj = [ MyObject  new ];      newObj .x  = obj .x  * obj .x ;        return   newObj; }

Now MyObject(Objective-C)’s variables and functions are directly accessed from javascript.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

JSContext  * context = [[ JSContext  alloc ]  init ]; NSString  * jsCode = @"function sqrtOf(obj){ return MyObject.getSqure(obj);}" ;        //adding Objective-C Class to Javascript.      context[ @"MyObject" ]=[ MyObject  class ];        [context  evaluateScript :jsCode];        MyObject  * obj =[ MyObject  new ];      obj .x  = 1 0 ;        JSValue  * func =context[ @"sqrtOf" ];      JSValue  * val = [func  callWithArguments :@[obj]];        //we got MyObject from javascript.      MyObject  *sqrtObj = [val  toObject ];        NSLog( @"Value =%d, %d" , obj .x , [sqrtObj  getX ]);