How to join two collections in a json store? - ibm-mobilefirst

Question

I am working on IBM Worklight. I need to access data from two collections. Is there any solution for joining the 2 collections and get the required fields ?

Answer 1

JSONSTORE does not have the ability to combine collections.
However the follow blog post details one way to achieve this: https://mobilefirstplatform.ibmcloud.com/blog/2015/02/24/working-jsonstore-collections-join/
Create a collection:
var OrdersCollection = {
orders: {
searchFields: {
order_id: 'integer',
order_date: 'string'
},
additionalSearchFields: {
customer_id: 'integer'
}
}
};
var CustomerCollection = {
customers: {
searchFields: {
customer_name : 'string',
contact_name : 'string',
country : 'string'
},
additionalSearchFields : {
customer_id : 'integer'
}
}
};
Add data using additional search fields:
var data = [
{order_id : 462, order_date : '1-1-2000'},
{order_id: 608, order_date : '2-2-2001'},
{order_id: 898, order_date : '3-3-2002'}
];
var counter = 0;
var q = async.queue(function (task, callback) {
setTimeout(function () {
WL.JSONStore.get('orders').add(task.data, {additionalSearchFields: {customer_id: task.customer_id}});
callback(++counter);
},0);
},1);
for(var i = 0; i < data.length; i++){
q.push({data : data[i], customer_id: i+1}, function(counter){
console.log("Added Order Doc " + counter);
});
}
q.drain = function(){
setTimeout(function() {
console.log("Finished adding order documents");
WL.JSONStore.get("orders").findAll({filter : ["customer_id", "order_id", "order_date"]})
.then(function (res) {
ordersCollectionData = res;
document.getElementById("orders").innerHTML = JSON.stringify(res, null, "\t");
})
.fail(function (err) {
console.log("There was a problem at " + JSON.stringify(err));
});
},0);
};
Find the documents to merge:
WL.JSONStore.get('orders').findAll({filter : ['customer_id', 'order_id', 'order_date']})
.then(function (res) {
ordersCollectionData = res;
});
Merge
var shared_index = 'customer_id';
var mergedCollection = [];
mergedCollection =_.merge(customerCollectionData, ordersCollectionData, function(a, b){
if(_.isObject(a) && (a[shared_index] == b[shared_index])) {
return _.merge({}, a, b);
}
});