The nestjs docs describe two main approaches for injecting dependencies, constructor-based and property-based injection. It's also mentioned that constructor-based injections should be preferred over property-based injection where possible without any description why.
Is there any specific reason for this or is it just some kind of code style guide?
WARNING If your class doesn't extend another provider, you should always prefer using constructor-based injection.
The nestjs docs does mention the reason to always prefer constructor-based injection. It states that if your class doesn't extend another provider then we should always use constructor-based injection.
What this means is that if your class has optional dependencies then you can use property-based injection otherwise you have to use constructor-based injection.
Consider, Class A which depends on Class B and Class A will not work if Class B is not injected in this case this is a mandatory dependency hence we have to use constructor-based injection.
Whereas, same Class A also depends on Class C but Class A will still work if Class C is not injected in this case it is an optional dependency hence we can use property-based injection here.
You can read more about this here:
https://khalilstemmler.com/articles/tutorials/dependency-injection-inversion-explained/ http://dillonbuchanan.com/programming/dependency-injection-constructor-vs-property/
Someone had asked the same thing on their discord but the answer isn't super clear... Here's a screenshot of the conversation:
