Updated June 12, 2023
Definition of Rails find_by
Rails find_by is an option to find any field records in a given table. Find_by helps to find the first matching record with the user-specified condition. Also, there is no specified order of finding the record matching the conditions given. Instead, if the order of findings is needed, the user will specify the order. Finally, the term “nil” will be displayed if no record matches the specified condition. In a nutshell, Ruby rails find_by helps to find the records in the set of data available.
Overview of Rails find_by
Rails are using ruby metaprogramming. In rails, there are many ways to find records. But all these methods use object-relational mapping (ORM) to map the query with the database. For instance, find, find_by, and some help find records. In this blog, we will study the find_by method of searching records in detail. Even if we use different methods, the same SQL will be generated. It is also the same for finding multiple records as well. The main difference between where and find_by is that find_by returns only one record; we will get all the matching records in the where method.
Find_by returns an object and where returns a collection. In find, we use to review a row by its ID. Find_by is a helper if we find a record or information within a column. It will map the search with its naming convention. For example, if we are naming a column with the heading “cost,” then the syntax should be as follows:
Model.find_by(cost:"Monthly")The alternative syntax is as follows:
find_by(:cost, "Monthly")Both the above codes can be executed in Rails.
How does find_by work?
There are three simple steps in the model find_by works.
The first step is giving the input parameter a key or value.
For Example:
User.find_by name: 'Smith', email: '[email protected]'If the given attribute is found in the second step, it will return the record. If the record is not found, it will return nil. If we want to raise ActiveRecord::RecordNotFound, we must use the find_by method. In the above example, if it finds the email id [email protected] in the specific column, it will return the matching email id. If not, it will return nil. But the return type in this method always objects.
Why find_by method?
If we are thinking of working on a model like updating some data, then only one record is being retrieved, where the id is unknown, then find_by will help in such a case because this method retrieves the record and will not put in an array. One such example to explain this concept is shown below:
irb(main):037:0> @kit = Kit.find_by(number: "1426")
Kit Load (0.9ms) SELECT "kits".* FROM "kits" WHERE "kits"."number" =
'1426' LIMIT 1
=> #<Kit id: 1, number: "1426", created_at: "2021-05-12 03:20:56",
updated_at: "2021-05-12 03:20:56", job_id: nil>
irb(main):038:0> @kit.update(job_id: 2)
(0.2ms) BEGIN Kit Exists (0.4ms) SELECT 1 AS one FROM "kits" WHERE
("kits"."number" = '3456' AND "kits"."id" != 1) LIMIT 1 SQL (0.5ms)
UPDATE "kits" SET "job_id" = $1, "updated_at" = $2 WHERE "kits"."id" =
1 [["job_id", 2], ["updated_at", Tue, 12 May 2015 07:16:58 UTC +00:00]]
(0.6ms) COMMIT => trueModel find_by will accept the array, but the drawback is that it will process only the first value in the array. For example:
Model.find_by_id([1,2,3])
How to Create find_by_attributes in rails?
The attributes will be returned as an output based on the attributes present in the find_by method. But it always returns the first object only. In the below example, find_by_attribute is used to find args. If args (arguments) are not found, then nil will be returned as output; hence, the code is shown below as an example.
Example:
def find_by_attributes(match, attributes, *args)
conditions = Hash[attributes.map {|a| [a, args[attributes.index(a)]]}]
result = where(conditions).send(match.finder)
if match.bang? && result.nil?
raise RecordNotFound, "Couldn't find #{@klass.name} with #{conditions.to_a.collect {|p| p.join(' = ')}.join(', ')}"
else
yield(result) if block_given?
result
endMethods used to search a record
The other advantage of using Rails find_by is that other than “nil,” which is displayed when no matching record is found, we can write syntax where it can display “No records found.” This is one advantage of using find_by over other methods. Though this method has its advantage, it has its disadvantage when compared with other methods, in which method it will display the collection of data available. So, it is easier to know the number of similar data available in a given query or database. At the same time, this added advantage is not found in the find_by method in Rails ruby. The core application of the find_by method is that when an ID is given as a query for search in a database, then keyword argument ID will be passed. The SQL generated will be similar for all three methods. The object returned will be the same at the end. If the given query is not the same or not found, then Record is not found will be displayed as a result of using the find method, and nil will be displayed when find_by is used in the Ruby console.
Conclusion – Rails find_by
Thus, rails find_by returns the first item present in the database. There are different syntaxes to perform a similar function. Similarly, we saw about find_by. There are other syntax or methods in rails to find records in the database. They are known as where and find. All of them almost work similarly. But the major difference is that in find_by, it will either return the first attribute, which is matching, or it will return nil. In other methods, it is a bit different. Rails find_by also searches the keywords in a given array. It can search a record in a given column. Find_by is more explicit about the exceptions we want to raise. Find_by follows the bang method in the convention. So, this method raises an exception when it is called.
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