Dynamic Helper

[rkjha]

To render category in sidebar view, I want to use dynamic helper and
in the function I want to call a model to fetch categories from db.

dynamicHelper code :
categories:function(){
category.cat_by_id(null,function(cats,err){
if(!err){
console.log(cats);
return cats;
}
else{
return null;
}
});
},

view code :
<ul class="nav nav-list">
<% for(var index in categories){ %>
<li class="nav-header"><a href="/blog/cat/<%=
categories[index].id %>"></a><%= categories[index].cat_name%></li>
<% } %>
</ul>
But I cant found the result on view.
Plz help me.

[Geert Pasteels]

You can't have callbacks inside your helpers. They are mostly for formatting not for calling the database. You need to set this up in your route/middleware.

[tjholowaychuk]

3.x has app.locals.use(callback) which replaces dynamicHelpers, async
stuff in 3.x will be fine
but Geert is right, in 2.x you need to return something

[Edmund von der Burg]

On 9 May 2012 17:37, rkjha <rkjha...@gmail.com> wrote:
> To render category in sidebar view, I want to use dynamic helper and
> in the function I want to call a model to fetch categories from db.

You can't use callbacks in the dynamic helpers - the return value of
the function is what is used, the callbacks will run but their output
is ignored.

You'll have to load the categories before rendering the templates -
route middleware is useful for this - you'd have something like
(adapting your example):

function loadCategories (req,res,next) {
category.cat_by_id(null,function(cats,err){
if(!err){
 res.local('cats', cats);
next();
return cats;
}
else{
res.local('cats', cats);
next(null); // to continue processing
// next(err); // to abort processing
}
}
}


You'd then use this route middleware before calling any page that
needs a sidebar

app.get('/has/a/sidebar', loadCategories, function (req,res) { ... });

see http://expressjs.com/guide.html#route-middleware for more details

PS: If you are happy to abort processing the request on an error then
the code can be shortened to:

function loadCategories (req,res,next) {
category.cat_by_id(null,function(cats,err){
res.local('cats', cats);
next(err); // if err is true will abort, otherwise continue
}
}

NOTE: in cat_by_id you have (cats,err) but convention would be to do (err,cats)

Cheers,
Edmund

> dynamicHelper code :
> categories:function(){
>    category.cat_by_id(null,function(cats,err){
>      if(!err){
>        console.log(cats);
>        return cats;
>      }
>      else{
>        return null;
>      }
>    });
>    },
>
> view code :
> <ul class="nav nav-list">
>        <% for(var index in categories){ %>
>          <li class="nav-header"><a href="/blog/cat/<%=
> categories[index].id %>"></a><%= categories[index].cat_name%></li>
>        <% } %>
>        </ul>
> But I cant found the result on view.
> Plz help me.
>

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[Edmund von der Burg]

On 9 May 2012 17:37, rkjha <rkjha...@gmail.com> wrote:

> To render category in sidebar view, I want to use dynamic helper and
> in the function I want to call a model to fetch categories from db.

> dynamicHelper code :
> categories:function(){
> category.cat_by_id(null,function(cats,err){
> if(!err){
> console.log(cats);
> return cats;
> }
> else{
> return null;
> }
> });
> },
>
> view code :
> <ul class="nav nav-list">
> <% for(var index in categories){ %>
> <li class="nav-header"><a href="/blog/cat/<%=
> categories[index].id %>"></a><%= categories[index].cat_name%></li>
> <% } %>
> </ul>
> But I cant found the result on view.
> Plz help me.
>

[Alan Hoffmeister]

Where can I read more about dynamicHelpers and usage example?

Thanks!

--
Att,
Alan Hoffmeister


2012/5/14 tjholowaychuk <tjholo...@gmail.com>: