在實(shí)際中，我們可以在注釋中定義好接口，在實(shí)際的代碼中予以實(shí)現(xiàn)
比如：
代碼如下: /*
interface Composite {
function add(child);
function remove(child);
function getChild(index);
}
interface FormItem {
function save();
}
*/
var CompositeForm = function(id, method, action) { // implements Composite, FormItem
...
};
// Implement the Composite interface.
CompositeForm.prototype.add = function(child) {
...
};
CompositeForm.prototype.remove = function(child) {
...
};
CompositeForm.prototype.getChild = function(index) {
...
};
// Implement the FormItem interface.
CompositeForm.prototype.save = function() {
...
};
實(shí)現(xiàn)接口的程序員是否將這些接口都實(shí)現(xiàn)了呢？我們沒(méi)辦法保證！因?yàn)檫@里沒(méi)有任何辦法去檢查是否都實(shí)現(xiàn)了
我們需要一個(gè)檢查是否實(shí)現(xiàn)了接口的機(jī)制，可以這樣：
代碼如下: /*
interface Composite {
function add(child);
function remove(child);
function getChild(index);
}
interface FormItem {
function save();
}
*/
var CompositeForm = function(id, method, action) {
this.implementsInterfaces = ['Composite', 'FormItem'];
...
};
...
function addForm(formInstance) {
if(!implements(formInstance, 'Composite', 'FormItem')) {
throw new Error("Object does not implement a required interface.");
}
...
}
// The implements function, which checks to see if an object declares that it
// implements the required interfaces.
function implements(object) {
for(var i = 1; i < arguments.length; i++) { // Looping through all arguments
// after the first one.
var interfaceName = arguments[i];
var interfaceFound = false;
for(var j = 0; j < object.implementsInterfaces.length; j++) {
if(object.implementsInterfaces[j] == interfaceName) {
interfaceFound = true;
break;
}
}
if(!interfaceFound) {
return false; // An interface was not found.
}
}
return true; // All interfaces were found.
}
這種方法讓程序員在寫的時(shí)候注明實(shí)現(xiàn)了哪些接口： this.implementsInterfaces = ['Composite', 'FormItem']; 在調(diào)用的時(shí)候使用implements方法來(lái)判斷是否實(shí)現(xiàn)了，理論上可行，很有可能寫上了實(shí)現(xiàn)了'Composite'接口，但是代碼里卻并沒(méi)有add方法！因此，我們需要檢驗(yàn)實(shí)現(xiàn)接口的類是否包含了接口里的方法！所以，接口必須從注釋中解放出來(lái)：
代碼如下: // Interfaces.
var Composite = new Interface('Composite', ['add', 'remove', 'getChild']);
var FormItem = new Interface('FormItem', ['save']);
// CompositeForm class
var CompositeForm = function(id, method, action) { // implements Composite, FormItem
...
};
...
function addForm(formInstance) {
Interface.ensureImplements(formInstance, Composite, FormItem);
// This function will throw an error if a required method is not implemented,
