Merge pull request #566 from thewhitetulip/patch-7

updated more information about template

en/07.4.md

@@ -380,6 +380,81 @@ When you don't want to use `{{define}}`, then you can just create a text file wi
 
 Templates in one set know each other, but you must parse them for every single set.
 
+Some times you want to contextualize templates, for instance you have a `_head.html`, you might have a header who's value you have to populate based on which data you are loading for instance for a todo list manager you can have three categories `pending`, `completed`, `deleted`. for this suppose you have an if statement like this 
+
+    <title>{{if eq .Navigation "pending"}} Tasks 
+           {{ else if eq .Navigation "completed"}}Completed
+           {{ else if eq .Navigation "deleted"}}Deleted
+           {{ else if eq .Navigation "edit"}} Edit
+           {{end}}
+     </title>
+     
+Note: Go templates follow the Polish notation while comparison where you give the operator first and the comparison value and the value to be compared with. The else if part is pretty straight forward
+
+Typically we use a `{{ range }}` operator to loop through the context variable which we pass to the template while execution like this:
+    
+    //present in views package
+    context := db.GetTasks("pending") //true when you want non deleted notes
+    homeTemplate.Execute(w, context)
+We get the context object from the database as a struct object, the definition is as below
+
+    //Task is the struct used to identify tasks
+    type Task struct {
+    	Id      int
+    	Title   string
+    	Content string
+    	Created string
+    }
+    //Context is the struct passed to templates
+    type Context struct {
+    	Tasks      []Task
+    	Navigation string
+    	Search     string
+    	Message    string
+    }
+    
+    //present in database package
+    var task []types.Task
+    var context types.Context
+    context = types.Context{Tasks: task, Navigation: status}
+    
+    //This line is in the database package where the context is returned back to the view.
+    
+We use the task array and the Navigation in our templates, we saw how we use the Navigation in the template, 
+we'll see how we'll use the actual task array in our template.
+    
+Here in the `{{ if .Tasks }}` we first check if the Tasks field of our context object which we passed to the template
+while execution is empty or not, if it is not empty then we will range through that array to populate the title and
+content of Task. The below example is very important when it comes to looping through an array in a template, we
+start with the Range operator, then we can give any member of that struct as `{{.Name}}`, my Task structure has a
+Title and a Content, please note the capital T and C, they are exported names and they need to be capital unless you
+want to make them private.
+    
+    so {{ range .Tasks }}
+        {{ .Title }}
+        {{ .Content }}
+       {{ end }}
+       
+This block of code will print each title and content of the Task array. Below is a full example from github.com/thewhitetulip/Tasks home.html template.
+    
+    <div class="timeline">
+    {{ if .Tasks}} {{range .Tasks}}
+    <div class="note">
+      <p class="noteHeading">{{.Title}}</p>
+      <hr>
+      <p class="noteContent">{{.Content}}</p>
+      </ul>
+      </span>
+    </div>
+    {{end}} {{else}}
+    <div class="note">
+      <p class="noteHeading">No Tasks here</p>
+      <p class="notefooter">
+      Create new task<button class="floating-action-icon-add" > here </button> </p>
+    </div>
+    {{end}}
+
+
 ## Summary
 
 In this section, you learned how to combine dynamic data with templates using techniques including printing data in loops, template functions and nested templates. By learning about templates, we can conclude discussing the V part of the MVC architecture. In the following chapters, we will cover the M and C aspects of MVC.