nwsIFetchTry               package:nws               R Documentation

_I_t_e_r_a_t_e _T_h_r_o_u_g_h _V_a_l_u_e_s _o_f _a _n_e_t_W_o_r_k_S_p_a_c_e _V_a_r_i_a_b_l_e

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

     Create a function that acts as a destructive iterator over the
     values of the specified variable.

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

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

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

 .Object: a netWorkSpace class object.

   xName: character string specifying 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:

     The iterator function returned by the 'nwsIFetchTry' method takes
     no arguments, and works just like the 'nwsFetchTry' method,
     specified with the same arguments that were passed to
     'nwsIFetchTry' method. Note that the 'nwsIFind' and 'nwsIFindTry'
     methods are much more useful, since they provide the only way to
     iterate over values of a variable non-destructively. The
     'nwsIFetch' and 'nwsIFetchTry' methods are provided for
     completeness.

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

     'nwsFetchTry', 'nwsIFetch'

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

     ## Not run: 
     ws <- netWorkSpace('nws example')
     nwsStore(ws, 'x', 10)
     it <- nwsIFetchTry(ws, 'x', NA)
     it()  # returns the value 10
     it()  # returns NA
     ## End(Not run)

