JavaScript实现依赖注入
var
cache = {};
// 通过解析Function.prototype.toString()取得参数名
function
getParamNames(func) {
// 正则表达式出自http://krasimirtsonev.com/blog/article/Dependency-injection-in-JavaScript
var
paramNames = func.toString().match(/^
function
\s*[^\(]*\(\s*([^\)]*)\)/m)[1];
paramNames = paramNames.replace(/ /g,
''
);
paramNames = paramNames.split(
','
);
return
paramNames;
}
var
injector = {
// 将func作用域中的this关键字绑定到bind对象上,bind对象可以为空
resolve:
function
(func, bind) {
// 取得参数名
var
paramNames = getParamNames(func);
var
params = [];
for
(
var
i = 0; i < paramNames.length; i++) {
// 通过参数名在cache中取出相应的依赖
params.push(cache[paramNames[i]]);
}
// 注入依赖并执行函数
func.apply(bind, params);
}
};
function
Notebook() {}
Notebook.prototype.printName =
function
() {
console.log(
'this is a notebook'
);
};
function
Pencil() {}
Pencil.prototype.printName =
function
() {
console.log(
'this is a pencil'
);
};
function
Student() {}
Student.prototype.write =
function
(notebook, pencil) {
if
(!notebook || !pencil) {
throw
new
Error(
'Dependencies not provided!'
);
}
console.log(
'writing...'
);
};
// 提供notebook依赖
cache[
'notebook'
] =
new
Notebook();
// 提供pencil依赖
cache[
'pencil'
] =
new
Pencil();
var
student =
new
Student();
injector.resolve(student.write, student);
// writing...