how to solve following snippet implementation?

[Christian Thomas]

Hello,

currently I have started to reimplement my existing blog (it is a JSF app : www.chr-thomas.de) with Lift to learn it (I can simply use my existing services via jndi lookup do get the appropriate content for the page). 

I want to create a side bar, which should show a listing of all existing main-categories including its sub-categories (if you visit my page, you can see it on the right side under the header "Kategorien"). The visitor can click such a sub-category to the filter the result of article-previews on that page.

Kategorien
Administration ( main-category )

• JDK :: 1 ( sub-category )

Softwareentwicklung ( main-category )

• Java Enterprise Edition :: 1 ( sub-category )

Okay, if have startet to write for that part following html conent

<section>

<header><h3>Kategorien</h3></header>

<section class="lift:Categories.mainCategories">

<header><h4><span lift:bind="row:name">main category name</span></h4></header>

<ul>

<li class="lift:Categories.subCategories"><a subrow:link=""><span lift:bind="subrow:name">sub category name</span></a> :: <span lift:bind="subrow:count">count</span></li>

</ul>

</section>

</section>

Here the snippet class:

class Categories {

def mainCategories(html: NodeSeq) : NodeSeq = {

val resource = new BlogResource // know's how to access the java services

val mainCategories = resource.getAllMainCategories

return mainCategories.flatMap(category => bind("row", html,        "name" -> {category.getName + " : " + category.getId}))

}

def subCategories(html: NodeSeq) : NodeSeq = {

val resource = new BlogResource // know's how to access the java services

val parentId : Long = 1 // for the first test a static id is set

val subCategories = resource.getAllChildCategories(parentId)

return subCategories.flatMap(category => bind("subrow", html,       FuncAttrBindParam("link", {ns : NodeSeq => Text("/blog/category/" + category.getName.toLowerCase)}, "href"),

      "name" -> {category.getName},

"count" -> {resource.getNoOfArticlesForCategory(category.getId)}))

}

}

[Christian Thomas]

oops, I have accidentally post it...

Okay, here my question:

How can I solve it in Lift:

I have to pass the id of each main-category to the snippet, which generates the entries for the sub-categories ( currently a static known parentId

val parentId : Long = 1 //in method subCategories

 is set to see, I the rest of the code works ) ?

Can give someone me a hint, example?

Thanks!

Kind regards!

Christian

[AGYNAMIX Torsten Uhlmann]

Hi Christian,

so you basically want to support a URL like "/blog/<xyz>/list" where xyz is a category or ID or whatever narrows down the elements to show?

Then Menu.param is one (preferred) solution to do it. Have a look at: https://github.com/d6y/london_class_march_2011_sitemap_css

You might need to put the source code into a new sbt skeleton project, but it still works with the latest Lift libs. There is an example David did with a list of forums and a list of threads per forum.

Does that help?

Torsten.

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[David Pollak]

Also, please use the CSS Selector Transforms rather than the bind() syntax... the CSS Selector Transforms lead to more readable and understandable code.

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[Christian Thomas]

@Torsten big thanks for your help via mail :thumbsup:

@Torsten, @David: yes, the css selector transforms is the better way. This also simply solved my problem.

Now the html look's like:

<section class="lift:Categories">

  <header><h4><span name="main-category-name">main category name</span></h4></header>

  <ul>

    <li name="sub-category"><a href="todo"><span name="sub-category-name">sub category name</span></a> :: <span name="sub-category-count">count</span></li>

  </ul>

</section>

and the snippet code:

class Categories {

def render = {

val resource = new BlogResource // know's how to access the java service

val mainCategories = resource.getAllMainCategories

"* *" #> mainCategories.map {mainCategory =>

"@main-category-name" #> mainCategory.getName &

"@sub-category *" #> resource.getAllChildCategories(mainCategory.getId).map {subCategory =>

"@sub-category-name" #> subCategory.getName &

"@sub-category-count" #> resource.getNoOfArticlesForCategory(subCategory.getId)

}

}

}
}

and I really like it : )

Now I have to check, how to use the Menu.param to append the dynamic link's...

[David Pollak]

Please take a look at the project that Torsten pointed you to. Specifically, the ForumStuff.scala file which contains the logic to create a menu link based on a parameter:

class AForum(f: Forum) {

  def render = "li *" #>

  ForumThread.all(f).map(t =>

    "a *+" #> t.name & "a [href]" #> AThread.menu.calcHref(f -> t))

[Christian Thomas]

Currently I'm trying to find out, how it work's. But at this first time it is really hard to understand, what there happens (the concrete impl) !

In my example I have got a page blog.html. This contains the snippet above to show the existing categories. Each rendered sub-category is clickable to filter the summary of listed blog-articles.

For instance:

/blog <-- has to show all existing blog-article-previews on the blog.html page

/blog/category/example <-- has to show all blog-article-previews in relation to the category "example" on the blog.html page

/blog/article/example-article <-- has to show the complete article on the article page ( I think I have to create an article folder containing a star.html file )

I have created a small mvn project (contains a lift-app and a tiny Java-Service (in real world it should be an EJB or something else...) ), which shows the current state of my test-project.

Please feel free to have a look on it: https://github.com/Chris81T/learning-lift.git

This version is still running without error's. May someone can support me to solve my current problem by giving some hints / example code (with may some short comments) appropriate to the small project. 

For instance I really don't understand following code:

object AForum {

  lazy val menu = 

    Menu.param[Forum]("AForum", // for what is this string good for? Simply a label

                      Loc.LinkText(f => Text(S.?("Forum") +": "+f.name)), // ?????

                      (s: String) => { // is this an anonymous function ??

                        println("Looking up forum "+s)

                        val ret = Forum.find(s)

                        println("Found "+ret)

                        ret // where will the return ret value be used ??

                        },

                      (f: Forum) => f.id) / "forums" / * // this defines the dynamic url. the id will be replaced for the *

}

Thank's in advance!

Christian

[Christian Thomas]

Okay, now I have continued implementing my example project.

First of all I simply want to create the article navigation:

• behind the "read..." link an appropriate url for the article is requested
• after clicking the "read..." link the article page has to be called and has to show the whole article instead of the article-preview on the blog page

  def render = {

/*

TODO:

- adapt class to support filtering by category

- add dynamic href article url

*/

/*

it is not necessary to return all real articles including content. It should be overhead. Only the complete

article is requested, if the visitor wants to read the article

--> An articlePreview knows the id of the article

*/

val articles = asScalaList(BlogJavaService.getAllArticlePreviews)

"* *" #> articles.map {article =>

"@article-title" #> article.getTitle &

"a [href]" #> Article.menu.calcHref(BlogJavaService.getArticle(article.getArticleId)) // TODO this is a first test to see, if something at all will work !!! Normally I do not want to call each article! I'm not really shure, how the Menu.param work's !!!

}

  }

this is the render function of the ArticlePreviews snippet. This is used to show on the blog page all existing article-previews (or all previews appropriate to a selected category ( filter function ))

Here is the Article object:

object Article {

/*

*  sealed trait MenuSingleton extends AnyRef

   * def param[T <: AnyRef](name: String, linkText: LinkText[T], parser: (String) ⇒ Box[T], encoder: (T) ⇒ String): PreParamMenu[T]

*/

lazy val menu = Menu.param[de.java.entities.Article]("Article",

"Reading an article",

                                                    articleId => findArticleById(articleId),

                                                    article => getIdForArticle(article)

) / "article" / *

def findArticleById(articleId: String) : Box[de.java.entities.Article] = {

val article = BlogJavaService.getArticle(articleId.toLong)

/* TODO I dont think, that is the best solution to get the box instance - source:

https://github.com/d6y/london_class_march_2011_sitemap_css/blob/master/src/main/scala/code/model/Forum.scala -> def find

*/

val map = Map(articleId -> article)

println("Found article=" + article + " for given id=" + articleId)

val box = map.get(articleId)

println("Returning created box=" + box)

box

}

def getIdForArticle(article: de.java.entities.Article) : String = {

val id = article.getId.toString

println("Returning requested id=" + id + " of article=" + article)

id

}

}

This code will create the required dynamic url's for each "read..." link on the blog page (my first success for that topic). But another solution should be better:

I think I have only to handle the articleId of each article-preview instance to create the url's. And if the user will click the "read..." link, then the whole article has to be loaded.

How do I have to change the Article.menu to solve this? 

To see the complete code, please clone my repository: https://github.com/Chris81T/learning-lift.git

Christian