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    Get Compare Exchange Value Operation

    Examples

    Get cmpXchg item that has a number and metadata:

    // Put a new compare-exchange item,
// e.g. save the number of sales made by an employee as the value + some metadata info        
const putCmpXchgOp = new PutCompareExchangeValueOperation("employees/1-A", 12345, 0,{
    "Department": "Sales",
    "Role": "Salesperson",
});
const result = await documentStore.operations.send(putCmpXchgOp);

// Get the compare-exchange item:
// ==============================

// Define the get compare-exchange operation, pass the unique item key
const getCmpXchgOp = new GetCompareExchangeValueOperation("employees/1-A");

// Execute the operation by passing it to operations.send
const item = await documentStore.operations.send(getCmpXchgOp);

// Access the value and metadata of the retrieved item
const numberOfSales = item.value;
const employeeRole = item.metadata["Role"];

// Access the version number of the retrieved item
const version = item.index;

    Get cmpXchg item that has an object:

    // Put a new compare-exchange item,
// e.g. save an object as the value
const employee = new Employee();
employee.role = "Salesperson"
employee.department = "Sales";
employee.numberOfSales = 12345;

const putCmpXchgOp = new PutCompareExchangeValueOperation("employees/1-A", employee, 0);
const result = await documentStore.operations.send(putCmpXchgOp);

// Get the compare-exchange item:
// ==============================

// Define the get compare-exchange operation, pass the unique item key & the class type
const getCmpXchgOp = new GetCompareExchangeValueOperation("employees/1-A", Employee);

// Execute the operation by passing it to operations.send
const item = await documentStore.operations.send(getCmpXchgOp);

// Access the value of the retrieved item
const employeeResult = item.value;
const employeeClass = employeeResult.constructor;   // Employee

const employeeRole = employeeResult.role;           // Salesperson
const employeeDep = employeeResult.department;      // Sales
const employeeSales = employeeResult.numberOfSales; // 12345

// Access the version number of the retrieved item
const version = item.index;
    class Employee {
    constructor(
        id = null,
        department = "",
        role = "",
        numberOfSales = 0

    ) {
        Object.assign(this, {
            id,
            department,
            role,
            numberOfSales
        });
    }
}

    Syntax 

    const getCmpXchgOp = new GetCompareExchangeValueOperation(key, clazz, materializeMetadata);
    Parameter Type Description
    key string The unique identifier of the cmpXchg item.
    clazz object The class type of the item's value.
    materializeMetadata boolean The Metadata will be retrieved and available regardless of the value of this param. Used for internal purposes. 

    // Return value of store.operations.send(getCmpXchgOp)
// ===================================================
class CompareExchangeValue {
    key;
    value;
    metadata;
    index;
}
    Parameter Type Description
    key string The unique identifier of the cmpXchg item.
    value object The existing value of the returned cmpXchg item.
    metadata object The existing metadata of the returned cmpXchg item.
    index number The compare-exchange item's version.

    related articlesRelated Articles

    Compare Exchange

    Client API

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