msg:context_exists

March 26, 2020 Contributors

Name

msg:context_exists — Check if a context variable exists

Synopsis

msg:context_exists(type, key);

type: numeric
key: string

Description

Check if a context variable exists. Legal values for type are:

  • msys.core.ECMESS_CTX_MESS

  • msys.core.ECMESS_CTX_CONN

local e = msg:context_exists(msys.core.ECMESS_CTX_MESS, 'key')

This function returns 1 if the key exists and 0 if the key does not exist.

The return value of this function should always be compared explicitly. For example:

local e = msg:context_exists(msys.core.ECMESS_CTX_MESS, 'key')
if e == 1 then
  -- do something here that depends on the key existing
end

Note that Lua treats the numeric value 0 as true, which can be confusing.

Because this function is in the msys.core namespace, an explicit require('msys.core') is not necessary.

See Also

msg:context_exists_and_get