coldfusion - ColdFusion 是否支持委托(delegate)？

Question

我有几个包含在 try/catch block 中的数据库访问方法:

function GetAll() {
    try {
        entityLoad("Book");
    }
    catch (any e) {
        throw (type="CustomException", message="Error accessing database, could not read");
    }
}

function Save(Book book) {
    try {
        entitySave(book);
    }
    catch (any e) {
        throw (type="CustomException", message="Error accessing database, could not save);
    }
}

如您所见，try/catch block 重复了几次，唯一不同的是消息。是否可以在 ColdFusion 中创建一个委托(delegate)，以便我可以改为执行类似的操作(使用 C# lambda 来表示匿名委托(delegate))？:

function GetAll() {
    DatabaseOperation(() => entityLoad("Book"), "could not read");
}

function Save(Book book) {
    DatabaseOperation(() => entitySave(book), "could not save");
}

function DatabaseOperation(delegate action, string error) {
    try {
        action.invoke();
    }
    catch (any e) {
        var message = "Error accessing database, " & error;
        throw (type="CustomException", message=message);
    }
}

Answer 1

基于您的示例，而不是 CF9。

CF10 即将推出闭包功能，您可以这样做:

function GetAll() {
    DatabaseOperation( closure(){ entityLoad("Book") } , "could not read");
}

function Save(Book book) {
    DatabaseOperation( closure(){ entitySave(book) } , "could not save");
}

function DatabaseOperation(closure action, string error) {
    try {
        action();
    }
    catch (any e) {
        var message = "Error accessing database, " & error;
        throw (type="CustomException", message=message);
    }
}

(语法可能会有所不同，不记得是否完全一样)

或者，我猜你可以在这里使用 evaluate ......

function GetAll() {
    DatabaseOperation( 'entityLoad("Book")' , "could not read");
}

function Save(Book book) {
    DatabaseOperation( 'entitySave(book)' , "could not save");
}

function DatabaseOperation(string action, string error) {
    try {
        evaluate(action);
    }
    catch (any e) {
        var message = "Error accessing database, " & error;
        throw (type="CustomException", message=message);
    }
}

就我个人而言，我只是删除 try/catch 并在 Application.cfc 中使用 onError - 似乎对掩盖原始错误没有用，而是抛出一个更通用的错误？

更新:另外两个可能的选择...

当前可行的另一个选项是拥有一个公共(public)包装函数，该函数调用 DatabaseOperation 函数，传入执行实际逻辑的私有(private)函数的名称，如下所示:

function GetAll() {
    DatabaseOperation( real_GetAll , Arguments , "could not read");
}
private function real_GetAll() {
    entityLoad("Book")
}

function Save(Book book) {
    DatabaseOperation( real_Save , Arguments , "could not save");
}
private function real_Save(Book book) {
    entitySave(book)
}

function DatabaseOperation(any action, struct args , string error) {
    try {
        action( argumentcollection=args )
    }
    catch (any e) {
        var message = "Error accessing database, " & error;
        throw (type="CustomException", message=message);
    }
}

如果您不喜欢两次定义函数的想法，但不介意模糊 API，您可以将方法设置为私有(private)，然后使用 onMissingMethod:

private function GetAll()
{
    entityLoad("Book")
}

private function Save(Book book)
{
    entitySave(book)
}

function onMissingMethod( string MethodName , struct MethodArgs )
{
    if ( NOT StructKeyExists(Variables,Arguments.MethodName) )
    {
        throw("The method #Arguments.MethodName# was not found");
    }

    try
    {
        var Meth = Variables[Arguments.MethodName];
        Meth( ArgumentCollection=Arguments.MethodArgs );
    }
    catch(any e)
    {
        var message = "Error accessing database, ";

        switch(MethodName)
        {
            case "GetAll":
                message &= "could not read";
            break;
            case "Save":
                message &= "could not save";
            break;
        }

        throw (type="CustomException,message=message);
    }
}