Neste capítulo, apresentaremos a peça final do quebra-cabeça que une os padrões Repositório e Camada de Serviço: o padrão Unidade de Trabalho.
Se o padrão Repository é a nossa abstração sobre a ideia de armazenamento persistente, o padrão Unit of Work (UoW) é a nossa abstração sobre a ideia de operações atómicas. Ele nos permitirá finalmente e completamente desacoplar nossa camada de serviço da camada de dados.
AFigura 6-1 mostra que, atualmente, ocorre muita comunicação entre as camadas da nossa infraestrutura: a API fala diretamente com a camada da base de dados para iniciar uma sessão, fala com a camada do repositório para inicializarSQLAlchemyRepository, e fala com a camada do serviço para lhe pedir para alocar.
Dica
O código para este capítulo está no ramo chapter_06_uow no GitHub:
git clone https://github.com/cosmicpython/code.git
cd code
git checkout chapter_06_uow
# or to code along, checkout Chapter 4:
git checkout chapter_04_service_layer
Figura 6-1. Sem UoW: A API fala diretamente com três camadas
A Figura 6-2 mostra nosso estado alvo. A API do Flask agora faz apenas duas coisas: inicializa uma unidade de trabalho e invoca um serviço. O serviço colabora com o UoW (gostamos de pensar no UoW como sendo parte ...
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