1. The Fluent Interface Pattern
Lars-Erik Kindblad
Senior Consultant
Blog: kindblad.com

2. A common problem in most software projects
 Technical debts increases over time and the code gets harder and
harder to maintain and add features to
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3. Feature delivery for most projects
Technical debt
Complex and messy code
Code and logic is duplicated
No common coding standard
Features Delivered
No strict architecture
++
Time
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4. Ideal Feature Delivery
Features Delivered
Time
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5. How to reach ideal delivery?
 Software development is complex
 Not a single solution but a mix of many different things
• Write a lot of code
• Important to understand the business model
• Readable & maintainable code over fancy code
• Simplicity over complexity
• Decide on a common coding standard
• Reuse code instead of code duplication
• Create a project framework with common code and logic
• Design Patterns – follow generic solutions to commonly occurring problems
o 100s of design patterns exists
– Factory Pattern, MVC Pattern, Command Pattern, Fluent Interface Pattern etc.
• ++
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6. The Fluent Interface Pattern
 One of many design patterns that can contribute to a better code
base
 Fluent Interfaces makes the code easier to read and easier to use
due to a simpler API that requires less code
 Consists of 2 principles:
• Method chaining - Traditional code requires one line per command, method
chaining allows multiple commands per line
• More readable API – The code can be read like a sentence. Optional as it
requires more typing due to longer names and more code to write
 Popular to use in frameworks: Moq, Fluent Nhibernate, FluentData
etc.
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7. Example – Find a person
Traditional Code:
Fluent Interface Code:
Or:
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8. A more readable Fluent Interface
Or:
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9. Designing Fluent Interfaces - Method vs. Property
Use a method when having to
accept one or more values
Use a property when not having
to accept any values
Use a method to finish the call
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10. Traditional Code
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11. Fluent Interface Code
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12. Example #2 – A List of Persons
Traditional Code:
Fluent Code:
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13. Traditional Code
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14. Fluent Interface Step 1: Add Gateway Pattern
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15. Step 2: Add Fluent Interface Pattern
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16. Examples from other Frameworks
Moq:
FluentData:
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17. When to use Fluent Interfaces
 Anywhere where it makes the code easier to read and easier to use
 Typically in methods that are often invoked
 Together with the Gateway Pattern to hide complex 3rd party code or
legacy code
 Frameworks
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18. QUESTIONS?
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