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working-with-nodes-api-service.md

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Working with the Nodes API service
Intermediate
2019-12-17

Working with the Nodes API Service

In this tutorial you will learn how to use the NodesApiService.

We have developed some practical examples to show you how to interact with an instance of Alfresco Content Services without using the REST endpoints directly. With this approach the NodesApiService is used as an abstraction layer, defined by one of the services in the ADF Core library.

Contents

Preparing the development environment

To focus the description on the NodesApiService, we will develop on top of the Alfresco Example Content Application. If you don't have it already installed in your development environment then see the prerequisites section in creating your first ADF Application.

When you have the Alfresco Example Content Application up and running, edit the FileComponent defined in src/app/components/files/files.component.ts. Change the navigateTo method to match the source code below.

if (node.isFile) {
    this.myOnNodeDoubleClick(node.id);
}

Now add the myOnNodeDoubleClick method as described below and save the file:

myOnNodeDoubleClick(nodeId) {
    console.log("You ckicked on the node '" + nodeId + "'.");
}

This will change the user experience when you click on a content node (but not a folder): in the browser's console you will see something like the following screenshot, instead of the preview of the content:

nodesapiservices_myonnodedoubleclick

The Alfresco Example Content app is now set up to demonstrate the usage of the NodesApiService.

Basic examples of usage

For a first look at the NodesApiService, let's check the FileComponent component stored in src/app/components/files/files.component.ts. In the source code, you can see the nodesApi property that represents the NodesApiService in the FilesComponent. See the fetchNode and fetchNodes methods for some very basic examples.

About the NodesApiService

Before going further, let's introduce the NodesApiService class. As you can see, the available methods are easy to understand and they should be all you need to manage the nodes of your content repository.

Observables

Almost all the methods return an Observable. Observables provide support for passing messages between publishers and subscribers in Angular applications. Observables offer significant benefits over other techniques for event handling, asynchronous programming, and handling multiple values.

The return values of the NodesApiService methods are managed in the usual way for Observables. You "subscribe" to the asynchronous messaging using the following syntax:

this.nodesApi.getNode(nodeId).subscribe(
    (node) => { ... },
    error => { ... }
);

MinimalNode

All the methods that manage content nodes return an Observable of the MinimalNode class. MinimalNode is used to represent the node's content. See the official documentation for further details.

NodePaging

When a method returns a list of nodes rather than a single node, it usually returns an Observable of the NodePaging class. See the NodePaging docs for further details.

Retrieving info and metadata from a node

As a first example of the usage of the NodesApiService, let's retrieve the properties of a content node using its identifier. Edit the myOnNodeDoubleClick method in src/app/components/files/files.component.ts, as shown below:

myOnNodeDoubleClick(nodeId) {
    this.nodesApi.getNode(nodeId)
    .subscribe(
        (node) => {
            console.log(node.properties);
        },
        error => { console.log("Ouch, an error happened!"); }
    );
}

This will show the properties of the content node in the browser's console as a log. The screenshot below shows an example of what this looks like:

nodesapiservices_properties

Of course, if you prefer to use the node's data in the user interface (using a DataTable or other visual component) then the principle is the same.

Retrieving the node's children

Another common use of the NodesApiService is to retrieve a list of the children of a folder node. Edit src/app/components/files/files.component.ts again, changing the navigateTo method to match the source code below:

    if (node.isFolder) {
	    this.myOnFolderNodeDoubleClick(node.id);
    }

Now add the myOnFolderNodeDoubleClick method as shown below and save the file:

myOnFolderNodeDoubleClick(nodeId) {
    this.nodesApi.getNodeChildren(nodeId)
    .subscribe(
        (nodePaging) => {
            console.log(nodePaging.list);
        },
        error => { console.log("Ouch, an error happened!"); }
    );
}

Now, the user experience changes if you click on a folder node (but not a content node) in the browser's console you will see something like the following screenshot:

nodesapiservices_nodeList

Creating and deleting a subfolder

The NodesApiService class is not just for retrieving data. You can also use it to manage a real CRUD of nodes (content and folders). In the following examples, you will see how to create a subfolder of the double clicked folder and also how to delete it.

Creating a subfolder

To create a subfolder, change the myOnFolderNodeDoubleClick method as described below and save the Typescript file.

myOnFolderNodeDoubleClick(nodeId) {
    this.nodesApi.createFolder(nodeId, { "name": "My new subfolder" })
    .subscribe(
        (node) => {
            console.log("Subfolder created with name '" + node.name + "' (id:'" + node.id + "').");
        },
        error => { console.log("Ouch, an error happened!"); }
    );
}

The user experience now changes if you click on a folder node (but not a content node). To check it out, double click on the Shared folder and in the browser's console you will see something like the following screenshot:

nodesapiservices_createnode

A new subfolder named My new subfolder will be created. You can check its existence using Alfresco Share client or by replacing the content of the myOnFolderNodeDoubleClick method with:

this.navigate(nodeId);`

...and then saving and navigating to the Shared folder.

In the following screenshot you can see how the browser should look:

nodesapiservices_createnode_proof

Note that if you double-click several times on a folder then the action should only succeed for the first click. The behaviour is correct if you bear in mind that you are trying to create folders with the same name in the same parent folder, which is not permitted by Alfresco Content Services.

Deleting a folder

To delete a folder, change the myOnFolderNodeDoubleClick method as described below and save the Typescript file.

myOnFolderNodeDoubleClick(nodeId) {
    this.nodesApi.deleteNode(nodeId)
    .subscribe(
        success => {
            alert("Node deleted! Click on a folder into the left menu.");
        },
        error => { console.log("Ouch, an error happened!"); }
    );
}

NOTE: This task could delete entire parts of your Alfresco repository if you double click on the wrong folder. Test it carefully!

Now, if you click on a folder node (be careful which folder you choose!) then you will see something like the following screenshot in the browser:

nodesapiservices_deletefolder

You can check that the folder does not exist anymore using Alfresco Share client or by replacing the content of the myOnFolderNodeDoubleClick method with

this.navigate(nodeId);

...and saving the file.