Fluent interface Wikipedia

You can also map and configure the properties of your domain classes using Fluent API. With default convention, Code First will create the database tables with the name of DbSet properties in the context class such as Courses, Enrollments and Students. But if you want different table names then you can override this convention and can provide a different table name than the DbSet properties, as shown in the following code.

Here I am using StringBuilder to store the actual string content of the dockerfile and the setters are essentially just adding content to this string builder. As you can see, my constructor is private which initializes a new object and I have a factory method that returns a new object. Besides the brute enforcement of a protocol, a fluent API also integrates neatly with certain IDE services. Auto-completion is a common IDE feature that suggests possible code continuations.

The users of an API are other programmers, who enjoy simple and intuitive interfaces that support error management, for when things are going bad. You can create such a relationship by defining a third table, called PHP 8 10 Answer a junction table, whose primary key consists of the foreign keys from both table A and table B. Instances of the entity type will not be able to be saved to the database unless this relationship is specified.

As a result, the StudentCourses table is created with Course_CourseID and Student_ID columns as shown in the following image. You can have a one entity class that maps to multiple tables from the same database . For example, Product data model will have details for Product as well as it’s inventory details. However at database level Products and Product inventory details needs to be in separate tables. While fluent APIs can be implemented in dynamic programming languages , they are especially potent in static languages (like Java and C++). One reason may be that the syntax of static languages tends to be more strict and cumbersome, so fluent chains spare the programmer a bit more hassle.

Their usage is demonstrated with a simple number list that is filtered, transformed and collected. For One-To-Many relationship, it’s possible to configure the relationship using both ends of the relationship. On the example below, I implemented in both ways to show as an example. Following code sets Maximum length for ProductName column as 50 characters. If you need to configure Primary Key with more than one column of the table. Use Sitefinity CMS Fluent API by referencing specific namespaces, defined in Telerik.Sitefinity.dll assembly.

  • The example below defines a class Employee and three methods to set its name, surname and salary.
  • In most cases, the Entity Framework can infer which type is the dependent and which is the principal in a relationship.
  • For all the methods in this interface, they can call their methods again or use the WithCommand method to break out of it.
  • For One-To-Many relationship, it’s possible to configure the relationship using both ends of the relationship.
  • In typed languages, using a constructor requiring all parameters will fail at compilation time while the fluent approach will only be able to generate runtime errors, missing all the type-safety checks of modern compilers.

So any exhortations to use them can only be preliminary – however I do think they are ripe for more experimentation. Now if we use the same fluent class, we get in a way guided tour of the natural order of methods and the methods we have at our disposal. Here are a few examples of the awesome code completion we get with this fluent class. One is the entry method like CreateBuilder() above or Initialize(). Although not really required , these are important in setting up the skeleton of the underlying object. The second one is the exit method like ToList() in LINQ or GenerateDockerFile() here which gives the actual result.

For example, filtering posts based on properties of their author. A few months ago I attended a workshop with Eric Evans, and he talked about a certain style of interface which we decided to name a fluent interface. It’s not a common style, but one we think should be better known. For all the methods in this interface, they can call their methods again or use the WithCommand method to break out of it.


It is based on the Fluent API design pattern where results are captured using method chaining. We are going to create interfaces to limit the next set of methods an object can call or what methods are allowed to be called at a particular time. Then our class would implement our interfaces and the methods would change their return types from the class to the respective interfaces thus giving us the better, guided flow we want. Nevertheless, fluent APIs in static programming languages can detect API abuses as early as compilation time. For example, our mail API forbids a call to from() to be followed by a subject() call, as it skips the senders field (to()). Registers an entity type as part of the model and returns an object that can be used to configure the entity.

But you can also override this convention, as shown in the following code. Entity Splitting lets you combine data coming from multiple tables into a single class and it can only be used with tables that have a one-to-one relationship between them. Let’s take a look at the following example in which Student information is mapped into two tables. You can use the HasDefaultSchema method on DbModelBuilder to specify the database schema to use for all tables, stored procedures, etc. Instances of the entity type will be able to be saved to the database without this relationship being specified. In PHP, one can return the current object by using the $this special variable which represent the instance.

It also contradicts the “fail-fast” approach for error protection. In the Java Swing API, the LayoutManager interface defines how Container objects can have controlled Component placement. One of the more powerful LayoutManager implementations is the GridBagLayout class which requires the use of the GridBagConstraints class to specify how layout control occurs.

Viscous Interface, where due to the above 3, the interface loses its fluency over time. Let’s try to see the order of methods that we can call using a state diagram . We are going to use Interfaces to solve all the problems listed above. For example in LINQ, whenever you call the OrderBy() method, that method gives you new methods that you are able to call like .ThenBy() or .ThenByDescending().

The Better Way to Create a Fluent API

It is necessary to set Maximum length for each string column to avoid truncation or business rules violation. If application tries to insert/update string length with more than configured length Entity Framework will throw DbEntityValidationException. The only requirement for chaining is that the previous function call must return only a single object (e.g. as returned by a findUnique query or a “to-one relation” like profile.user()). The fluent API lets you fluently traverse the relations of your models via function calls. Note that the last function call determines the return type of the entire query . Are available for relation fields when using the model’s create or update query.

fluent api

The example below defines a class Employee and three methods to set its name, surname and salary. Each return the instance of the Employee class allowing to chain methods. Method chaining – calling a method returns some object on which further methods can be called. Another way to create the One-to-many relationship it’s by the fully defined relationships.

Disconnect a related record

The way of doing this is similar to the previous approach, but we also need to create an “Id” property that is related to the related object. Fluent API method IsFixedLength allows you to configure properties to create columns with fixed lengths. The application must provide value with the exact number of characters as mentioned in MaxLength. Space will be added if the length of value is less than the configured value of MaxLength.

fluent api

Certainly chaining is a common technique to use with fluent interfaces, but true fluency is much more than that. Building a fluent API like this leads to some unusual API habits. This convention does get in the way of a fluent interface, so I’m inclined to suspend the convention for this case. The best start to discussing the benefits and pitfalls of creating a fluent API comes for the example itself that we took. As you can see, designing a fluent API is really domain specific like the example was really specific to the domain of generating a dockerfile and this is what Martin Fowler believes as well. This requirement of the domain knowledge forces you to think as a user of your API, how well your API communicates with the users and is critical to the success of it as well.

As you can see, after you create the builder, the first method should be FromImage() to set the base image. You can cycle through any of the states, i.e. any state should be reachable Software development articles for dummies from any other state. From all of these states, you should be able to reach the penultimate state that can set the container startup command using the WithCommand() method.

Code Against Interfaces, Not Implementations

This is especially useful when we want to create a chain of commands and allow the client to apply these as required. In fluent APIs like StringBuilder discussed above, any combination of method calls can compile, even if it breaks the protocol. To avoid run-time errors, we have to state the protocol details in the class documentation . Once this line of code has been added, you no longer need to remember to add new type configuration registrations to the OnModelCreating method as your model grows. The Fluent API provides a larger range of configuration options than Data Annotation attributes. Fluent API configuration also facilitates cleaner code, in that the configuration can be kept separate from the domain classes.

Create multiple records and multiple related records

Fluent interface can also be used to chain a set of method, which operates/shares the same object. Instead of creating a customer class, we can create a data context which can be decorated with fluent interface as follows. If you use the Code First naming conventions, in most cases you can rely on Code First to set up relationships between your tables based on the foreign keys and navigation properties. The Property method is used to configure attributes for each property belonging to an entity or complex type. The Property method is used to obtain a configuration object for a given property.

Creating APIs with Python Free 19-Hour Course provides more functionality for configuration than DataAnnotations. The Code First Fluent API is most commonly accessed by overriding the OnModelCreating method on your derived DbContext. A simple way to do this in JavaScript is using prototype inheritance and this. Let’s start to configure entities using Fluent API in the next chapter.

So far we’ve mostly seen fluent APIs to create configurations of objects, often involving value objects. I’m not sure if this is a defining characteristic, although I suspect there is something about them appearing in a declarative context. The key test of fluency, for us, is the Domain Specific Language quality. The more the use of the API has that language like flow, the more fluent it is. We can now model these stages as interfaces now, and use the transition between these stages to determine the return type of each methods. You can also see the setter method FromImage that adds content to the object and returns it back, which will enable us to use “method-chaining” on our objects.

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