nwsFetchTry               package:nws               R Documentation

_F_e_t_c_h _a _V_a_l_u_e _f_r_o_m _a _N_e_t_W_o_r_k_S_p_a_c_e (_N_o_n-_B_l_o_c_k_i_n_g _V_e_r_s_i_o_n)

_D_e_s_c_r_i_p_t_i_o_n:

     Attempt to fetch a value associated with a variable from the
     shared netWorkSpace;  a non-blocking version of 'nwsFetch'.

_U_s_a_g_e:

     ## S4 method for signature 'netWorkSpace':
     nwsFetchTry(.Object, xName, defaultVal=NULL)

_A_r_g_u_m_e_n_t_s:

 .Object: a netWorkSpace class object

   xName: name of the variable to be fetched

defaultVal: value to return, if xName is not found in the netWorkSpace

_D_e_t_a_i_l_s:

     Look in the shared netWorkSpace for a value bound to 'xName'.  If
     found, remove a value associated with 'xName' from the shared
     netWorkSpace. This operation is atomic. If there are multiple 
     nwsFetch or nwsFetchTry requests for a given 'xName', any given
     value from  the set of values associated with 'xName' will be
     returned to just one requester. 

     If variable is not found, return immediately rather than block on
     the  operation (as in the case of 'nwsFetch'). If variable is not
     found,  the value of argument 'defaultVal' is returned. By
     default, 'defaultVal' is 'NULL'.

_S_e_e _A_l_s_o:

     'nwsDeclare', 'nwsFetch'

_E_x_a_m_p_l_e_s:

     ## Not run: 
     ws <- netWorkSpace('nws example')
     # If variable 'x' is not found in the shared netWorkSpace,
     # return default value, NULL.
     nwsFetchTry(ws, 'x')
     # If variable 'x' is not found in the shared netWorkSpace, 
     # return 10.
     nwsFetchTry(ws, 'x', 10)
     ## End(Not run)

