Filter

The Filter class is a helper class that focuses on filter-related concerns. It provides methods for creating and applying filters in queries.

getPreciseValues

Retrieves precise values for each property in a filter for an entity.

returns:

A promise that resolves to a FilterPreciseValues object containing the precise values for each property.

example:

const preciseValues = await Filter.getPreciseValues(meta, {
  status: { $ne: 'active' },
  $or: [
    { customerId: ["1", "2"] },
    { customerId: "3" }
  ]
});
console.log(preciseValues);
// Output:
// {
//   "customerId": ["1", "2", "3"], // Precise values inferred from the filter
//   "status": undefined,           // Cannot infer precise values for 'status'
// }

Arguments:

• metadata - The metadata of the entity being filtered.
• filter - The filter to analyze.

getPreciseValues

Retrieves precise values for each property in a filter for an entity.

returns:

A promise that resolves to a FilterPreciseValues object containing the precise values for each property.

example:

const preciseValues = await where.getPreciseValues();
console.log(preciseValues);
// Output:
// {
//   "customerId": ["1", "2", "3"], // Precise values inferred from the filter
//   "status": undefined,           // Cannot infer precise values for 'status'
// }

createCustom

Creates a custom filter. Custom filters are evaluated on the backend, ensuring security and efficiency. When the filter is used in the frontend, only its name is sent to the backend via the API, where the filter gets translated and applied in a safe manner.

returns:

A function that returns an EntityFilter of type entityType.

example:

class Order {
 //...
 static activeOrdersFor = Filter.createCustom<Order, { year: number }>(
   async ({ year }) => {
     return {
       status: ['created', 'confirmed', 'pending', 'blocked', 'delayed'],
       createdAt: {
         $gte: new Date(year, 0, 1),
         $lt: new Date(year + 1, 0, 1),
       },
     }
   },
 )
}
// Usage
await repo(Order).find({
 where: Order.activeOrders({ year }),
})

see:

Sql filter and Custom filterFiltering and Relations

Arguments:

• translator - A function that returns an EntityFilter.
• key - An optional unique identifier for the custom filter.

entityFilterToJson

Translates an EntityFilter to a plain JSON object that can be stored or transported.

returns:

A plain JSON object representing the EntityFilter.

example:

// Assuming `Task` is an entity class
const jsonFilter = Filter.entityFilterToJson(Task, { completed: true });
// `jsonFilter` can now be stored or transported as JSON

Arguments:

• entityDefs - The metadata of the entity associated with the filter.
• where - The EntityFilter to be translated.

entityFilterFromJson

Translates a plain JSON object back into an EntityFilter.

returns:

The reconstructed EntityFilter.

example:

// Assuming `Task` is an entity class and `jsonFilter` is a JSON object representing an EntityFilter
const taskFilter = Filter.entityFilterFromJson(Task, jsonFilter);
// Using the reconstructed `EntityFilter` in a query
const tasks = await remult.repo(Task).find({ where: taskFilter });
for (const task of tasks) {
  // Do something for each task based on the filter
}

Arguments:

• entityDefs - The metadata of the entity associated with the filter.
• packed - The plain JSON object representing the EntityFilter.

fromEntityFilter

Converts an EntityFilter to a Filter that can be used by the DataProvider. This method is mainly used internally.

returns:

A Filter instance that can be used by the DataProvider.

example:

// Assuming `Task` is an entity class and `taskFilter` is an EntityFilter
const filter = Filter.fromEntityFilter(Task, taskFilter);
// `filter` can now be used with the DataProvider

Arguments:

• entity - The metadata of the entity associated with the filter.
• whereItem - The EntityFilter to be converted.

constructor

• new Filter

Arguments:

• apply

resolve

Resolves an entity filter.

This method takes a filter which can be either an instance of EntityFilter or a function that returns an instance of EntityFilter or a promise that resolves to an instance of EntityFilter. It then resolves the filter if it is a function and returns the resulting EntityFilter.

returns:

The resolved entity filter.

Arguments:

• filter - The filter to resolve.

toJson

• toJson