zoukankan      html  css  js  c++  java

  • 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: Download source of Execute JavaScript in iOS Application

    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.
    - (int32_t)toInt32;
     
    // The value is copied to an integer according to the conversion specified by
    // the JavaScript language.
    - (uint32_t)toUInt32;
     
    // 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:10],[NSNumber numberWithInt:20]];
        JSValue * ret =[func callWithArguments:args];
        NSLog(@"10+20 = %d", [ret toInt32]);
     
        //function without arguments
        NSString * jsCode2 = @"function getRandom() { return parseInt(Math.floor((Math.random()*100)+1));} ";
        [context evaluateScript:jsCode2];
     
        JSValue * func2 =context[@"getRandom"];
     
        for(int i=0;i<5;i++)
        {
            JSValue * ret2 =[func2 callWithArguments:nil];
            NSLog(@"Random Value = %d", [ret2 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 arg1,int arg2)
        {
            return arg1+arg2;
        };
     
        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()%100;
        };
     
        NSString * jsCode2 =@"getRandom();";
        for(int i=0;i<5;i++)
        {
            JSValue * sumVal2 = [context evaluateScript:jsCode2];
            NSLog(@"Random Number = %d", [sumVal2 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 =10;
     
        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]);
     
    转：http://hayageek.com/execute-javascript-in-ios/
  • 相关阅读:
    枚举--分巧克力--蓝桥杯--二分法
    枚举笔记之哈希表 四个平方和
    枚举 蓝桥杯 四个平方数和2--暴力解法 超时
    枚举例题之平方十位数思路无代码
    LeetCode----盛最多水的容器「贪心」
    2020校招笔试
    2020校招美团点评笔试
    2020校招搜狗笔试
    2020网易校招笔试
    2020校招途家名宿开发笔试
  • 原文地址：https://www.cnblogs.com/ygm900/p/4317509.html
Copyright © 2011-2022 走看看