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文章摘自： http://www.cocoachina.com/ios/20150127/11037.html
JSContext/JSValue
JSContext 即JavaScript代码的运行环境。一个Context就是一个JavaScript代码执行的环境，也叫作用域。当在浏览器中运行 JavaScript代码时，JSContext就相当于一个窗口，能轻松执行创建变量、运算乃至定义函数等的JavaScript
//Objective-CJSContext *context = [[JSContext alloc] init];[context evaluateScript:@"var num = 8 + 5"];[context evaluateScript:@"var names = [‘Grace‘, ‘Ada‘, ‘Margaret‘]"];[context evaluateScript:@"var triple = function(value) { return value * 3 }"];JSValue *tripleNum = [context evaluateScript:@"triple(num)"];NSLog(@"Tripled: %d", [tripleNum toInt32]); //Swiftlet context = JSContext()context.evaluateScript("var num = 5 + 5")context.evaluateScript("var names = [‘Grace‘, ‘Ada‘, ‘Margaret‘]")context.evaluateScript("var triple = function(value) { return value * 3 }")let tripleNum: JSValue = context.evaluateScript("triple(num)")println("Tripled: \(tripleNum.toInt32())")
JSValue *names = context[@"names"];JSValue *initialName = names[0];NSLog(@"The first name: %@", [initialName toString]);//Swiftlet names = context.objectForKeyedSubscript("names")let initialName = names.objectAtIndexedSubscript(0)println("The first name: \(initialName.toString())")//Objective-CJSValue *tripleFunction = context[@"triple"];JSValue *result = [tripleFunction callWithArguments:@[@5] ];NSLog(@"Five tripled: %d", [result toInt32]);//Swiftlet tripleFunction = context.objectForKeyedSubscript("triple")let result = tripleFunction.callWithArguments([5])println("Five tripled: \(result.toInt32())")//Objective-Ccontext.exceptionHandler = ^(JSContext *context, JSValue *exception) { NSLog(@"JS Error: %@", exception);};[context evaluateScript:@"function multiply(value1, value2) { return value1 * value2 "];// JS Error: SyntaxError: Unexpected end of script//Swiftcontext.exceptionHandler = { context, exception in println("JS Error: \(exception)")}context.evaluateScript("function multiply(value1, value2) { return value1 * value2 ")// JS Error: SyntaxError: Unexpected end of scriptJavaScript函数调用
了 解了从JavaScript环境中获取不同值以及调用函数的方法，那么反过来，如何在JavaScript环境中获取Objective-C或者 Swift定义的自定义对象和方法呢？要从JSContext中获取本地客户端代码，主要有两种途径，分别为Blocks和JSExport协议。
Blocks （块）
在JSContext中，如果Objective-C代码块赋值为一个标识 符，JavaScriptCore就会自动将其封装在JavaScript函数中，因而在JavaScript上使用Foundation和Cocoa类 就更方便些——这再次验证了JavaScriptCore强大的衔接作用。现在CFStringTransform也能在JavaScript上使用了， 如下所示：
//Objective-Ccontext[@"simplifyString"] = ^(NSString *input) { NSMutableString *mutableString = [input mutableCopy]; CFStringTransform((__bridge CFMutableStringRef)mutableString, NULL, kCFStringTransformToLatin, NO); CFStringTransform((__bridge CFMutableStringRef)mutableString, NULL, kCFStringTransformStripCombiningMarks, NO); return mutableString;};NSLog(@"%@", [context evaluateScript:@"simplifyString(‘?????!‘)"]);//Swiftlet simplifyString: @objc_block String -> String = { input in var mutableString = NSMutableString(string: input) as CFMutableStringRef CFStringTransform(mutableString, nil, kCFStringTransformToLatin, Boolean(0)) CFStringTransform(mutableString, nil, kCFStringTransformStripCombiningMarks, Boolean(0)) return mutableString}context.setObject(unsafeBitCast(simplifyString, AnyObject.self), forKeyedSubscript: "simplifyString")println(context.evaluateScript("simplifyString(‘?????!‘)"))// annyeonghasaeyo!内存管理（Memory Management）
代码块可以捕获变量引用，而JSContext 所有变量的强引用都保留在JSContext中，所以要注意避免循环强引用问题。另外，也不要在代码块中捕获JSContext或任何JSValues， 建议使用[JSContext currentContext]来获取当前的Context对象，根据具体需求将值当做参数传入block中。
JSExport协议
借助JSExport协议也可以在JavaScript上使用自定义对象。在JSExport协议中声明的实例方法、类方法，不论属性，都能自动与JavaScrip交互。文章稍后将介绍具体的实践过程。
JavaScriptCore实践
我们可以通过一些例子更好地了解上述技巧的使用方法。先定义一 个遵循JSExport子协议PersonJSExport的Person model，再用JavaScript在JSON中创建和填入实例。有整个JVM，还要NSJSONSerialization干什么？
PersonJSExports和Person
Person类执行的 PersonJSExports协议具体规定了可用的JavaScript属性。，在创建时，类方法必不可少，因为JavaScriptCore并不适用 于初始化转换，我们不能像对待原生的JavaScript类型那样使用var person = new Person()。
//Objective-C// in Person.h -----------------@class Person;@protocol PersonJSExports @property (nonatomic, copy) NSString *firstName; @property (nonatomic, copy) NSString *lastName; @property NSInteger ageToday; - (NSString *)getFullName; // create and return a new Person instance with `firstName` and `lastName` + (instancetype)createWithFirstName:(NSString *)firstName lastName:(NSString *)lastName;@end@interface Person : NSObject @property (nonatomic, copy) NSString *firstName; @property (nonatomic, copy) NSString *lastName; @property NSInteger ageToday;@end// in Person.m -----------------@implementation Person- (NSString *)getFullName { return [NSString stringWithFormat:@"%@ %@", self.firstName, self.lastName];}+ (instancetype) createWithFirstName:(NSString *)firstName lastName:(NSString *)lastName { Person *person = [[Person alloc] init]; person.firstName = firstName; person.lastName = lastName; return person;}@end//Swift// Custom protocol must be declared with `@objc`@objc protocol PersonJSExports : JSExport { var firstName: String { get set } var lastName: String { get set } var birthYear: NSNumber? { get set } func getFullName() -> String /// create and return a new Person instance with `firstName` and `lastName` class func createWithFirstName(firstName: String, lastName: String) -> Person}// Custom class must inherit from `NSObject`@objc class Person : NSObject, PersonJSExports { // properties must be declared as `dynamic` dynamic var firstName: String dynamic var lastName: String dynamic var birthYear: NSNumber? init(firstName: String, lastName: String) { self.firstName = firstName self.lastName = lastName } class func createWithFirstName(firstName: String, lastName: String) -> Person { return Person(firstName: firstName, lastName: lastName) } func getFullName() -> String { return "\(firstName) \(lastName)" }}配置JSContext
创建Person类之后，需要先将其导出到JavaScript环境中去，同时还需导入Mustache JS库，以便对Person对象应用模板。
//Objective-C// export Person classcontext[@"Person"] = [Person class];// load Mustache.jsNSString *mustacheJSString = [NSString stringWithContentsOfFile:... encoding:NSUTF8StringEncoding error:nil];[context evaluateScript:mustacheJSString];//Swift// export Person classcontext.setObject(Person.self, forKeyedSubscript: "Person")// load Mustache.jsif let mustacheJSString = String(contentsOfFile:..., encoding:NSUTF8StringEncoding, error:nil) { context.evaluateScript(mustacheJSString)}JavaScript数据&处理
以下简单列出一个JSON范例，以及用JSON来创建新Person实例。
注 意：JavaScriptCore实现了Objective-C/Swift的方法名和JavaScript代码交互。因为JavaScript没有命名 好的参数，任何额外的参数名称都采取驼峰命名法（Camel-Case），并附加到函数名称上。在此示例中，Objective-C的方法 createWithFirstName:lastName:在JavaScript中则变成了 createWithFirstNameLastName()。
//JSON[ { "first": "Grace", "last": "Hopper", "year": 1906 }, { "first": "Ada", "last": "Lovelace", "year": 1815 }, { "first": "Margaret", "last": "Hamilton", "year": 1936 }]//JavaScriptvar loadPeopleFromJSON = function(jsonString) { var data = JSON.parse(jsonString); var people = []; for (i = 0; i < data.length; i++) { var person = Person.createWithFirstNameLastName(data[i].first, data[i].last); person.birthYear = data[i].year; people.push(person); } return people;}//Objective-C// get JSON stringNSString *peopleJSON = [NSString stringWithContentsOfFile:... encoding:NSUTF8StringEncoding error:nil];// get load functionJSValue *load = context[@"loadPeopleFromJSON"];// call with JSON and convert to an NSArrayJSValue *loadResult = [load callWithArguments:@[peopleJSON]];NSArray *people = [loadResult toArray];// get rendering function and create templateJSValue *mustacheRender = context[@"Mustache"][@"render"];NSString *template = @"{{getFullName}}, born {{birthYear}}";// loop through people and render Person object as stringfor (Person *person in people) { NSLog(@"%@", [mustacheRender callWithArguments:@[template, person]]);}// Output:// Grace Hopper, born 1906// Ada Lovelace, born 1815//Swift// get JSON stringif let peopleJSON = NSString(contentsOfFile:..., encoding: NSUTF8StringEncoding, error: nil) { // get load function let load = context.objectForKeyedSubscript("loadPeopleFromJSON") // call with JSON and convert to an array of `Person` if let people = load.callWithArguments([peopleJSON]).toArray() as? [Person] { // get rendering function and create template let mustacheRender = context.objectForKeyedSubscript("Mustache").objectForKeyedSubscript("render") let template = "{{getFullName}}, born {{birthYear}}" // loop through people and render Person object as string for person in people { println(mustacheRender.callWithArguments([template, person])) } }}// Output:// Grace Hopper, born 1906// Ada Lovelace, born 1815// Margaret Hamilton, born 1936
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原文地址：http://www.cnblogs.com/Ohero/p/4258960.html
