Question

我需要用erlang编写一个if语句，条件是在我接收的元组中搜索此测试“ tele / folin-house-s1 / SENSOR”。在下面插入要接收的元组：

{message,<<0,5,128,208,182,250,162,9,244,64,0,0,105,198,0,0>>,
     1,<<"DVES_0DBFDB">>,
     #{dup => false,retain => true},
     #{username => undefined},
     <<"tele/folin-house-s1/LWT">>,<<"Offline">>,
     {1549,8794,985040}}.
{message,<<0,5,128,208,182,250,162,9,244,64,0,0,105,198,0,0>>,
     1,<<"DVES_0DBFDB">>,
     #{dup => false,retain => true},
     #{username => undefined},
     <<"tele/folin-house-s1/LWT">>,<<"Offline">>,
     {1549,8794,985040}}.
{message,undefined,0,<<"733f0bfd-0741-4e55-bd14-ba10a156165f1549007325254">>,
     #{dup => false,retain => false},
     #{username => undefined},
     <<"tele/folin-house-s1/SENSOR">>,
     <<"{\"Time\":\"2018-12-18T22:37:00\",\"BME680\":{\"Temperature\":21.3,\"Humidity\":38.1,\"Pressure\":1021.4,\"Gas\":308.19},\"TempUnit\":\"C\"}">>,
     {1549,8796,895335}}.
{message,undefined,0,<<"733f0bfd-0741-4e55-bd14-ba10a156165f1549007325254">>,
     #{dup => false,retain => false},
     #{username => undefined},
     <<"tele/folin-house-s1/SENSOR">>,
     <<"{\"Time\":\"2018-12-18T22:37:00\",\"BME680\":{\"Temperature\":21.3,\"Humidity\":38.1,\"Pressure\":1021.4,\"Gas\":308.19},\"TempUnit\":\"C\"}">>,
     {1549,8803,302986}}.

我将使用if语句仅过滤这样的元组：

{message,undefined,0,<<"733f0bfd-0741-4e55-bd14-ba10a156165f1549007325254">>,
     #{dup => false,retain => false},
     #{username => undefined},
     <<"tele/folin-house-s1/SENSOR">>,
     <<"{\"Time\":\"2018-12-18T22:37:00\",\"BME680\":{\"Temperature\":21.3,\"Humidity\":38.1,\"Pressure\":1021.4,\"Gas\":308.19},\"TempUnit\":\"C\"}">>,
     {1549,8803,302986}}.

包含“ tele / folin-house-s1 / SENSOR”的

。我不知道erlang编码。

Answer 1

可能最好使用case子句

在这种情况下，您需要通过函数传递接收到的元组

这是函数示例：

message({message,_, _,_, _, _, <<"tele/folin-house-s1/LWT">>,_, _}) ->
  do_something();
message(_Tuple) -> skip.

这是带有'case'语句的示例：

message({message,_, _,_, _, _, Condition,_, _}) ->
  case Condition of
    <<"tele/folin-house-s1/LWT">> -> do_something();
    _Any -> skip
  end.

下面是带有'if'语句的示例：

message({message,_, _,_, _, _, Condition,_, _}) ->
  if
    Condition =:= <<"tele/folin-house-s1/LWT">> ->
      do_something();
    true ->
      skip
  end.

元组中带有搜索文本条件的if语句

1 个答案: