DI, dependency-injection, is a design pattern where dependencies (instances of objects, properties) of a component are set through the constructor(s), methods or fields (properties)

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So Singletons are bad, then what?

There has been a lot of discussion lately about the problems with using (and overusing) Singletons. I've been one of those people earlier in my career too. I can see what the problem is now, and yet, ...
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7answers
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What does the Spring framework do? Should I use it? Why or why not?

So, I'm starting a brand-new project in Java, and am considering using Spring. Why am I considering Spring? Because lots of people tell me I should use Spring! Seriously, any time I've tried to get ...
101
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4answers
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Difference between Dependency Injection (DI) and Inversion of Control (IOC)

I've been seeing a lot of references of Dependency Injection (DI) & Inversion Of Control (IOC), but I don't really know if there is a difference between them or not. I would like to start using ...
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18answers
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Dependency injection: How to sell it [closed]

Let it be known that I am a big fan of dependency injection (DI) and automated testing. I could talk all day about it. Background Recently, our team just got this big project that is to built from ...
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9answers
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Understanding dependency injection

I'm reading about dependency injection (DI). To me, it is a very complicated thing to do, as I was reading it was referencing inversion of control (IoC) as well and such I felt I was going to be in ...
66
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5answers
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When is it not appropriate to use the dependency injection pattern?

Since learning (and loving) automated testing I have found myself using the dependency injection pattern in almost every project. Is it always appropriate to use this pattern when working with ...
59
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10answers
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(Why) is it important that a unit test not test dependencies?

I understand the value of automated testing and use it wherever the problem is well-specified enough that I can come up with good test cases. I've noticed, though, that some people here and on ...
46
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5answers
12k views

Should I use Dependency Injection or static factories?

When designing a system I am often faced with the problem of having a bunch of modules (logging, database acces, etc) being used by the other modules. The question is, how do I go about providing ...
31
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7answers
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When NOT to apply Dependency Inversion?

I am currently trying to figure out SOLID. So Dependency inversion means that any two classes should communicate via interfaces, not directly. E.g. if class A has a method, that expects a pointer to ...
31
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3answers
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How does dependecy injection increase coupling?

On the Wikipedia page on dependency injection, the disadvantages section tells us this: Dependency injection increases coupling by requiring the user of a subsystem to provide for the needs of ...
26
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5answers
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What's the best way to build a factory using NInject?

I am pretty comfortable with dependency injection using NInject in MVC3. While working in an MVC3 application, I developed a custom Controller Creation Factory using NInject, so any controller that is ...
25
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11answers
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Does Refactoring towards Looser Coupling, Smaller Functions, and Separate Classes affect System Performance? (and Should I Care)

Lest you be confused by what's to follow, here is the driving idea behind the question: I always intended the question to be what it is. I may not have articulated it well originally. But intent ...
25
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4answers
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Does “Inversion of Control” promote “Anemic Domain Model”?

When I used IoC Container in my last project, I ended up with anemic entities and most of my business logic in Stateless Services. I have seen projects written by other developers that utilize ...
24
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3answers
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What is constructor injection?

I have been looking at the terms constructor injection and dependency injection while going through articles on (Service locator) design patterns. When I googled about constructor injection, I got ...
21
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4answers
6k views

Interception vs Injection: a framework architecture decision

There's this framework that I'm helping to design. There are some common tasks that should be done using some common components : Logging, Caching and raising events in particular. I am not sure if ...
19
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5answers
4k views

What are the benefits of dependency injection in cases where almost everyone needs access to a common data structure?

There are plenty of reasons why globals are evil in OOP. If the number or size of the objects needing sharing is too large to be efficiently passed around in function parameters, usually everyone ...
19
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6answers
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Dependency injection ; good practices to reduce boilerplate code

I have a simple question, and I'm not even sure it has an answer but let's try. I'm coding in C++, and using dependancy injection to avoid global state. This works quite well, and I don't run in ...
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6answers
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Should the usage of DI/IoC remove all occurrences of the “new” keyword?

Should the usage of Dependency Injection and an Inversion of Control container remove all occurrences of the "new" keyword from your code? In other words, should every object/dependency, no matter ...
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4answers
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Dependency Injection: Field Injection vs Constructor Injection?

I know this is a hot debate and the opinions tend to change over time as to the best approach practice. I used to use exclusively field injection for my classes, until I started reading up on ...
17
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3answers
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Sell me on IoC containers, please

I've seen several recommend use of IoC containers in code. The motivation is simple. Take the following dependency injected code: class UnitUnderTest { std::auto_ptr<Dependency> d_; public: ...
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8answers
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Is Dependency Injection worth it outside of UnitTesting

Given a constructor that will never, ever, have to use any different implementations of several objects that it initializes, is it still practical to use DI? After all, we might still want to unit ...
16
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3answers
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Legitimate “real work” in a constructor?

I am working on a design, but keep hitting a roadblock. I have a particular class (ModelDef) that is essentially the owner of a complex node tree built by parsing an XML schema (think DOM). I want to ...
16
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1answer
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Dependency Injection/IoC container practices when writing frameworks

I've used various IoC containers (Castle.Windsor, Autofac, MEF, etc) for .Net in a number of projects. I have found they tend to be frequently abused and encourage a number of bad practices. Are ...
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2answers
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Is DDD-Lite a pattern language for dependency injection?

I stumbled upon Greg Young's talk 7 Reasons why DDD Projects Fail where he mentions something he calls DDD-Lite at 7:20. Summarizing, he basically says some use DDD as a pattern languages (entities, ...
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2answers
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Domain-Driven-Design - external dependencies in the Entity problem

I'd like to start Domain-Driven-Design, but there are several problems I'd like to solve before starting :) Let's imagine I have a Groups and Users and when user wants to join a group, I'm calling ...
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4answers
972 views

Why do we need frameworks for dependency injection? [closed]

I've been reading up more on the Inversion of Control principle and Dependency Injection as an implementation of it and am pretty sure I understand it. It seems to be basically saying 'don't declare ...
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5answers
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Can I use Dependency Injection without breaking Encapsulation?

Here is my Solution and projects: BookStore (solution) BookStore.Coupler (project) Bootstrapper.cs BookStore.Domain (project) CreateBookCommandValidator.cs CompositeValidator.cs IValidate.cs ...
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6answers
743 views

Do abstractions have to reduce code readability?

A good developer I work with told me recently about some difficulty he had in implementing a feature in some code we had inherited; he said the problem was that the code was difficult to follow. From ...
14
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3answers
1k views

I get dependency injection, but can someone help me understand the need for an IoC container?

I apologize if this seems like yet another repeat of the question, but every time I find an article regarding the topic, it mostly just talks about what DI is. So, I get DI, but I'm trying to ...
14
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3answers
15k views

Which classes should be autowired by Spring (when to use dependency injection)?

I have been using Dependency Injection in Spring for some time now, and I understand how it works and what are some pros and cons of using it. However, when I'm creating a new class I often wonder - ...
13
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5answers
2k views

Does following TDD inevitably lead to DI?

I learned to do Test Driven Development (TDD), Dependency Injection (DI) and Inversion of Control (IoC) all at the same time. When I write code using TDD I always end up using DI in my class's ...
13
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5answers
3k views

When to use interfaces (unit testing, IoC?)

I suspect I've made a schoolboy error here, and am looking for clarification. A lot of the classes in my solution (C#) - dare I say the majority - I've ended up writing a corresponding interface for. ...
12
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4answers
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This way I'm writing this code is testable, but is there something wrong with it I'm missing?

I have an interface called IContext. For the purposes of this it doesn't really matter what's it does except the following: T GetService<T>(); What this method does is look at the current DI ...
12
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3answers
488 views

Do dependency injection frameworks pose a dependency risk?

I have been refactoring an existing system to use dependency injection, and that work has been going smoothly. After a while I noticed that a large number of in-house libraries became dependent upon ...
12
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2answers
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What is the difference between DI and IoC? [duplicate]

Possible Duplicate: Difference between Dependency Injection (DI) & Inversion of Control (IOC) I'm new to Inversion of Control, Dependency Injection and everything related to these ...
12
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5answers
802 views

C++: Should class own or observe its dependencies?

Say I have a class Foobar that uses (depends on) class Widget. In good ol' days, Widget wolud be declared as a field in Foobar, or maybe as a smart pointer if polymorphic behavior was needed, and it ...
11
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2answers
212 views

Anemic domain models and domain services injection

The anemic domain model is described as an anti-pattern in domain driven design by Martin Fowler. To have business logic on the domain models often domain services are used. But injecting domain ...
10
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4answers
11k views

Should one use Dependency Injection even if the class is used only once? [duplicate]

During a code review I have started having a bit of a dilemma as to whether use dependency injection or not. I would like to hear your thoughts, because this is kind of an ongoing theme and would help ...
10
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4answers
953 views

Gradual approaches to dependency injection

I'm working on making my classes unit-testable, using dependency injection. But some of these classes have a lot of clients, and I'm not ready to refactor all of them to start passing in the ...
10
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2answers
1k views

What's the practical difference between the styles of dependency injection?

I'm new to dependency injection and I have a few questions about which style I shouldI use in my applications. I've just read Inversion of Control Containers and the Dependency Injection pattern by ...
9
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2answers
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Problem with understanding “seam” word

I'm reading "Dependency Injection in .NET" by Mark Seemann (it's fantastic, and must have) and the author often uses the word "seam". But I can't understand what it means. Here is an example of using ...
9
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4answers
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Should injecting dependencies be done in the ctor or per method?

Consider: public class CtorInjectionExample { public CtorInjectionExample(ISomeRepository SomeRepositoryIn, IOtherRepository OtherRepositoryIn) { this._someRepository = ...
9
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2answers
8k views

Dependency injection with n-tier Entity Framework solution

I am currently designing an n-tier solution which is using Entity Framework 5 (.net 4) as its data access strategy, but am concerned about how to incorporate dependency injection to make it testable / ...
9
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3answers
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IValidatableObject vs Single Responsibility

I like the extnesibility point of MVC, allowing view models to implement IValidatableObject, and add custom validation. I try to keep my Controllers lean, having this code be the only validation ...
9
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4answers
6k views

Use Dependency Injection For Data Objects?

I'm just learning about dependency injection, and am stuck on something. Dependency Injection recommends sending dependent classes through the constructor, but I'm wondering if this is necessary for ...
9
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1answer
1k views

Multiple Zend application code organisation

For the past year I have been working on a series of applications all based on the Zend framework and centered on a complex business logic that all applications must have access to even if they don't ...
8
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3answers
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How is dependency injection not just moving the complexity into a separate class?

I've been looking into using the Typhoon framework for dependency injection this week. I get that separating the construction of objects is beneficial for replacing arbitrary components with mocks ...
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4answers
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How to use Dependency Injection in conjunction with the Factory pattern

Consider a module that is responsible for parsing files of any given type. I am thinking of using the strategy pattern to tackle this problem as I have already explained over here. Please refer to the ...
8
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5answers
700 views

How to TDD test that objects are being added to a collection if the collection is private?

Assume that I planned to write a class that worked something like this: public class GameCharacter { private Collection<CharacterEffect> _collection; public void Add(CharacterEffect e) ...
8
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4answers
649 views

What complexity do DI frameworks add?

The currently most upvoted answer to a very recent question states that DI containers are an "enterprise software" pattern, used when the object graph is very large and complex. I suspect that 95% ...