error-handling - InDesign CS5脚本: Why is `#targetengine` not working correctly?

Question

我知道Inoji会使用声明#targetengine "myEngineName"来记住全局变量(有关此信息，请参见http://incom.org/post/89818)。

但是，这仍然不足以使其记住全局变量，因为它仍然会引发有关全局变量imgs的错误:

Error Number:  30476
Error String:  "if(imgs[i].itemLink != null)" could not be completed because the object no longer exists.

...或类似的东西。它不喜欢我的代码中的那一行，似乎忘记了全局变量 imgs被实例化为什么。

因此，我实现了一条try-catch语句，并重新设置了变量 imgs并减小了catch中的迭代器...虽然可以解决此 问题，但#targetengine "myEngineName"为什么不能像预期的那样解决问题？

这是我的代码:

#target "InDesign" // this solves the "Error Number: 29446" problem
#targetengine "session" // this solves the "Error Number: 30476" problem

var imgs; // global variable for the #targetengine "session" to keep track of
var document = app.activeDocument;
var newFolder = createFolder(document); // if subdirectory images DNE, create this folder with the function below

saveAllImages(document, newFolder); // with the function below

alert("The file conversion is complete!\n\nAll black & white images have been copied to:\n" + newFolder +
        "\.\n\nAll color images have been replaced with the new black & white images in the current InDesign document.");

//---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

function createFolder(doc)
{
    try
    {
      /*
         * type-casting the filePath property (of type object) into a String type;
         * must be a String type to concatenate with the subdirectory variable (also of type String)
         */
        var docPath = String(doc.filePath);
        var subdirectory = "/BLACK AND WHITE IMAGES";
    }
    catch(e)
    {
        alert(e.message + "\n - reload the script, and it should work.");
        exit();
    }

    var imagesFolder = docPath + subdirectory; // concatenating the two variables
    if(!Folder(imagesFolder).exists)
    {
        Folder(imagesFolder).create();
    }

    return imagesFolder; // for instantiation outside of this function

} // end of function createFolder

//---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

function saveAllImages(doc, folder)
{
    imgs = document.allGraphics; // this is a global variable, for the #targetengine "session" to keep track of
    var fileName = "";
    var img = "";
    var imgType = "";

    for(var i = 0; i < imgs.length; i++)
    {
        try
        {
            if(imgs[i].itemLink != null)
            {
                fileName = imgs[i].itemLink.name;

                img = new File(folder + "/" + fileName); // each image instantiated here
                imgType = imgs[i].imageTypeName; // image type is determined here (.tif, .jpg, .png, etc..)

                //alert("The file \"" + fileName + "\"\n\tis a " + imgType + " file."); // Note: escape characters

               /*
                     * array for image options, instantiated from the function below;
                     * options[0] is the "MAXIMUM" image quality property, &
                     * options[1] is the "GRAY" image conversion property;
                     */
                var options = convertToBlackAndWhite(imgType);

                // each image exported to the new folder here, by file type
                switch(imgType)
                {
                    case "GIF":
                        alert("This script cannot convert and export the GIF file:\n\t" + fileName + " !"); // Note: escape characters
                        break;

                    case "Adobe PDF":
                        break;                            
                    case "EPS":
                        break;
                    case "Windows Bitmap":
                        break;
                    case "JPEG":
                        break;
                    case "PNG":
                        break;
                    case "TIFF":
                        options[0]; // maximum image quality
                        options[1]; // black & white conversion

                        imgs[i].exportFile(ExportFormat.JPG, img, false);
                        replaceWithNewImage(doc, fileName, img); // with the function below
                        break;

                    default:
                        alert("\tUnlisted image type: " + imgType + "!\nAdd this type to the switch statement.");
                        break;
                } // end of switch statement

            } // end of if statement
        } // end of try statement
        catch(e)
        {
            /*
                * in case the #targetengine is overloaded, this solves the "Error Number: 30476" problem:
                *           - "The requested action could not be completed because the object no longer exists."
                *               (the second statement #targetengine "session" is also in place to solve this error)
                */
            imgs = document.allGraphics; // global variable reinstantiated in case of error
            i--; // retry the same iteration again, in case of error (the variable " i " is the iterator in the for loop)
        }
    } // end of for loop

} // end of function saveAllImages

//---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

        function convertToBlackAndWhite(fileType)
        {
            // array for image-quality and color-conversion values
            var settings = [];

            // each image exported to the new folder here, by file type
            switch(fileType)
            {                    
                    case "Windows Bitmap":
                        break;
                    case "JPEG":
                        break;
                    case "PNG":
                        break;
                    case "TIFF":
                    settings[0] = "app.jpegExportPreferences.jpegQuality = JPEGOptionsQuality.MAXIMUM"; // maximum image quality
                    settings[1] = "app.jpegExportPreferences.jpegColorSpace = JpegColorSpaceEnum.GRAY"; // black & white conversion
                    break;

                default:
                    break;
            } // end of switch statement

            return settings; // for instantiation outside of this function

        } // end of function convertToBlackAndWhite

//---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

function replaceWithNewImage(doc, imageName, newImage)
{
    var links = doc.links;
    var link = "";
    for(var i = 0; i < links.length; i++)
    {
        link = links[i];
        if ( (link.status == LinkStatus.NORMAL) && (link.name == imageName) )
        {
            try
            {
                link.relink(newImage);
                link.update();
            }
            catch(e)
            {
            }
        } // end of if statement
    } // end of for loop

} // end of function replaceWithNewImage

这是我可以找到的有关此错误的唯一信息:http://forums.adobe.com/thread/748419

编辑-

我很确定问题与replaceWithNewImage函数有关，因为没有此函数就不会发生此错误，因此不需要try-catch语句...

Answer 1

阅读您的代码，我发现可能确实有问题。您将对文档的引用设置为 Activity 文档。但是此引用在整个 session 中仍然存在。事实是，如果您切换到另一个文档或关闭该文档，则引用将丢失。这也许可以解释为什么img有时会无法定义，尽管我认为它应该引发错误。
请将变量包装在函数范围内，我保证您一切都会好起来；)