CODEWITHSUNDEEP
reactjsreact-nativeamazon-dynamodb
Dunsany
Dunsany

Reputation: 53

React Native - How to connect to AWS DynamoDB table

I am following this aws tutorial to create my first React Native app which connects to AWS:

aws tutorial

Everything installs fine and my app runs happily with the following imports:

**import Amplify from 'aws-amplify';
import aws_exports from './aws-exports'; 
Amplify.configure(aws_exports);**

I would now like to connect the app to an existing DynamoDB table called 'Movement' but the tutorial only shows how to create a new table with the NoSQL wizard using: awsmobile database enable --prompt

Could you point me to a (simple) resource that shows me how to connect to an existing DynamoDB table and perform CRUD operations?

These are the steps I have followed:

I have a DynamoDB table called: movement It has 3 items : hub_id, on_time, message

Hub_id is the primary partition key on_time is the primary sort key

The table holds sensor data (movement, temperature that sort of thing) in the message item.

I created the app using :

create-react-native-app dbapp

I have then run: awsmobile configure aws mobile init

Installed amplify: npm install aws-amplify --save

I created the project in mobile hub.

I then linked the app to the hub using: awsmobile init 15c482e2-2c3c-11e8-8692-fblahblahblah3

CLI responded : Successfully linked AWS Mobile Hub project: dbapp-datetime!

So all looks good so far (I hope!)

I then altered app.js to look like this: pastebin

npm start runs just fine with no errors that I can see.

The problem that I currently have is that I don't have a clue about how to query my table and populate variables so that I can use them in the view.

Upvotes: 2

Views: 7209

Answers (1)

Dunsany
Dunsany

Reputation: 53

Following the resources suggested (thanks SteveB). I connected to the DynamoDB table, queried it and used the data in my app.

In case you are also stuck, here is an edited version of my code. Apologies to everyone that gets to edit this - I know it is awful. Does work though :)

      // Use db to query the dynamoDB table - setup query parameters first //


var params = {
    TableName : "myproject-mobilehub-123456789-Sensors",
    ProjectionExpression:"hub_id, details.on_time, details.sensor_name, 
details.temperature, details.battery",
    KeyConditionExpression: "hub_id = :hid AND begins_with(on_time, :d)",
    ExpressionAttributeValues: {
        ":hid":"testdevice01",
        ":d": today,
        },
    Limit: 1,
    ScanIndexForward: false
};

//Execute db query using params

    async getQuery() {
    db.query(params, function(err, data) {
    if (err) { console.log("Query failed.");
    } else {
        console.log("Query succeeded.");
    };

    data.Items.forEach(function(details) {

        //display variables

console.log(details.hub_id,details.details.sensor_name,details.details.on_time, 
details.details.temperature, details.details.battery,); 

        //Populate variables
        hubid = details.hub_id;
        currroom = details.details.sensor_name;
        roomtime = details.details.on_time;
        roomtemp = details.details.temperature;
        roombattery = details.details.battery + "%";
    });

}});

//Finally populate text with variables

this.setState({
  displayText1: currroom,
  displayText2: roombattery,
  displayText3: roomtime,
  displayText4: roomtemp

});

Upvotes: 2

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