operator-keyword

问题 Visual Studio 2019's code analysis and code suggestions started to highlight every line of code where I call a method that returns a value but don't use that value at all and tells me to use the discard operator _ . I don't fully understand why that matters and it even seems wrong for Fluent API style code. Is there a functional difference between the two following lines? private int SomeMethod() => 0; ... SomeMethod(); _ = SomeMethod(); ... Would it matter more if the return value is a

问题 In some programming languages, I see (ex.): x := y What is this := operator generally called and what does it do? 回答1: In all languages that support an operator := it means assignment. In languages that support an operator := , the = operator usually means an equality comparison. In languages where = means assignment, == is typically used for equality comparison. does := mean = ? I can't recall any languages where := means the same as = . In MySQL := and = are both used for assignment,

问题 This is a working code: String a = "first"; String b = "second"; String object; System.out.println(object != null ? a : b); But it isn't: String a = "first"; String b = "second"; String object; object != null ? System.out.println(a) : System.out.println(b); Why? 回答1: A per the spec It is a compile-time error for either the second or the third operand expression to be an invocation of a void method. println is a method from the PrintStream class (which System.out is an instance of) and it has

问题 I found in some C# source code the following line: if(!(context.Compilation.GetTypeByMetadataName("Xunit.FactAttribute") is { } factAttribute)) and here is another one: if(!(diagnostic.Location.SourceTree is { } tree)) What is the meaning of the curly braces ( { } ) after the is operator? 回答1: This is a new pattern matching feature which was introduced in C# 8.0 and is called property pattern. In this particular case it is used to check that object is not null, example from linked article:

问题 I found in some C# source code the following line: if(!(context.Compilation.GetTypeByMetadataName("Xunit.FactAttribute") is { } factAttribute)) and here is another one: if(!(diagnostic.Location.SourceTree is { } tree)) What is the meaning of the curly braces ( { } ) after the is operator? 回答1: This is a new pattern matching feature which was introduced in C# 8.0 and is called property pattern. In this particular case it is used to check that object is not null, example from linked article:

问题 I am trying to get DockerOperator work with Airflow on my Mac. I am running Airflow based on Puckel with small modifications. Dockerfile build as puckel-airflow-with-docker-inside: FROM puckel/docker-airflow:latest USER root RUN groupadd --gid 999 docker \ && usermod -aG docker airflow USER airflow docker-compose-CeleryExecutor.yml.: version: '2.1' services: redis: image: 'redis:5.0.5' postgres: image: postgres:9.6 environment: - POSTGRES_USER=airflow - POSTGRES_PASSWORD=airflow - POSTGRES_DB

问题 I am trying to get DockerOperator work with Airflow on my Mac. I am running Airflow based on Puckel with small modifications. Dockerfile build as puckel-airflow-with-docker-inside: FROM puckel/docker-airflow:latest USER root RUN groupadd --gid 999 docker \ && usermod -aG docker airflow USER airflow docker-compose-CeleryExecutor.yml.: version: '2.1' services: redis: image: 'redis:5.0.5' postgres: image: postgres:9.6 environment: - POSTGRES_USER=airflow - POSTGRES_PASSWORD=airflow - POSTGRES_DB

来源： https://stackoverflow.com/questions/63187528/why-does-rxjs-subscribe-allow-omitting-the-arrow-function-and-the-following-meth

来源： https://stackoverflow.com/questions/63187528/why-does-rxjs-subscribe-allow-omitting-the-arrow-function-and-the-following-meth

来源： https://stackoverflow.com/questions/63187528/why-does-rxjs-subscribe-allow-omitting-the-arrow-function-and-the-following-meth