mirror of https://github.com/tiangolo/fastapi.git
72 lines
2.2 KiB
Markdown
72 lines
2.2 KiB
Markdown
Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.
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## A `dict` from the previous example
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In the previous example, we where returning a `dict` from our dependency ("dependable"):
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```Python hl_lines="7"
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{!./src/dependencies/tutorial001.py!}
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```
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But then we get a `dict` in the parameter `commons` of the path operation function.
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And we know that `dict`s can't provide a lot of editor support because they can't know their keys and value types.
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## Create a Pydantic model
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But we are already using Pydantic models in other places and we have already seen all the benefits.
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Let's use them here too.
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Create a model for the common parameters (and don't pay attention to the rest, for now):
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```Python hl_lines="11 12 13 14"
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{!./src/dependencies/tutorial002.py!}
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```
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## Return a Pydantic model
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Now we can return a Pydantic model from the dependency ("dependable") with the same data as the dict before:
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```Python hl_lines="18"
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{!./src/dependencies/tutorial002.py!}
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```
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## Declare the Pydantic model
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We can now come back to the path operation function and declare the type of the `commons` parameter to be that Pydantic model:
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```Python
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commons: CommonQueryParams = Depends(common_parameters)
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```
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It won't be interpreted as a JSON request `Body` because we are using `Depends`:
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```Python hl_lines="22"
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{!./src/dependencies/tutorial002.py!}
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```
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!!! info
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In the case of dependencies with `Depends`, the type of the parameter is only to get editor support.
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Your dependencies won't be enforced to return a specific type of data.
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## Use the Pydantic model
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And now we can use that model in our code, with all the lovable editor support:
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```Python hl_lines="24 25 26"
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{!./src/dependencies/tutorial002.py!}
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```
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<img src="/img/tutorial/dependencies/image02.png">
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## Trees of hierarchical dependencies
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With the **Dependency Injection** system you can build arbitrarily deep trees of hierarchical dependencies (also known as dependency graphs) by having dependencies that also have dependencies themselves.
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You will see examples of these dependency trees in the next chapters about security.
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## Recap
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By using Pydantic models in your dependencies too you can keep all the editor support that **FastAPI** is designed to support. |