Box, call Query() with conditions as arguments:HasPrefix on a device location. Where does this come from? ObjectBox generates a Device_ struct for you to reference available properties conveniently. This also allows code completion in your IDE and avoids typos: correctness is checked at compile time (string based queries would only be checked at run-time).Device_ in the same package:Device_ to construct type-specific conditions in place and combining them, forming the full query. The following example looks for devices located in the U. S. with profile number 42.Query you should cache the Query object and re-use it. To make a Query more reusable you can change the values, or query parameters, of each condition you added even after the Query is built. Let's see how.User with specific FirstName values. First, we build a regular Query with an equal() condition for FirstName. Because we have to pass an initial parameter value to equal() but plan to override it before running the Query later, we just pass an empty string:Query. To set a value for the FirstName parameter we call setStringParams() on the Query and pass the FirstName property and the new parameter value:Alias() right after specifying the condition:Query has .Offset() and .Limit() methods to help you do thatOffset(n uint64): the first n results are skipped.
Limit(n uint64): at most n results of this query are returned.Equals(), NotEquals(), GreaterThan() and LessThan() there are also conditions like:Between() to filter for values that are between the given two (inclusive)In() and NotIn() to filter for values that match any in the given set,HasPrefix(), HasSuffix() and Contains() for extended String filtering.Find() returns a slice of the matching objects,FindIds()fetches just the IDs of the matching objects as a slice, which can be more efficient in case you don't need the whole object,Remove() deletes all the matching objects from the database (in a single transaction),Count() gives you the number of the objects that match the query,Limit() and Offset() let you select just part of the result (e. g. for paging)DescribeParams() is a utility function which returns a human-readable representation of the query.Person that can be associated with multiple Address entities:Person with a certain name that also lives on a specific street, we need to query the associated Address entities of a Person. To do this, use the Person_.Address.Link(cs ...Conditions) method of the generated Person_ variable to tell that the addresses relation should be queried and what conditions should be used to filter the addresses:Address instead of Person? No problem, links are smart enough to know there's also an implicit relation in the opposite direction. Note the different box we're using here:query.Property(Property) . For example, instead of getting all Users, to just get their email addresses:FindStrings() (and similar for other types) is a value to be used if the given field is nil in the database. By default, i.e. when you pass `nil` as the argument, these values are not returned. However, you can specify a replacement value to return if a property is null:Min() / MinDouble(): Finds the minimum value for the given property over all objects matching the query.Max() / MaxFloat64(): Finds the maximum value.Sum() / SumFloat64(): Calculates the sum of all values. Note: the integer version detects overflows and returns an error in that case.Average() : Calculates the average (always a float64) of all values.Count(): returns the number of results. This is faster than finding and getting the length of the result array. Can be combined with Distinct() to count only the number of distinct values.