nwsVariable-methods: Create an Active Binding for a netWorkSpace Variable

Description Usage Arguments Details Examples

Description

nwsVariable creates a variable in an R workspace that mirrors a variable in a netWorkSpace. This allows standard R operations (get, assign) to be used to share data between R programs running on different machines.

Usage

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  ## S4 method for signature 'netWorkSpace'
nwsVariable(.Object, xName, mode=c('fifo','lifo','multi','single'),env=parent.frame(),force=FALSE,quietly=FALSE)

Arguments

.Object

a netWorkSpace class object.

xName

name of variable to be declared.

mode

mode of the variable, see details.

env

environment in which to define active binding.

force

logical; if TRUE, an existing binding will be overwritten.

quietly

logical; if TRUE, no warnings are issued.

Details

nwsVariable is built on top of the R makeActiveBinding function. It is experimental, but we have found that it is very useful for introducing people to the concept of netWorkSpace variables. It's not clear that this API is ever preferable to nwsStore, nwsFetch, nwsFind for real programs, however.

The mode of the variable controls what happens when a variable is accessed. If the mode is 'single', then all accesses use the nwsFind operation. If the mode is 'fifo', 'lifo', or 'multi', then all accesses use the nwsFetch operation. Assigning a value to an nwsVariable always uses the nwsStore operation.

Examples

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  ## Not run: 
# create a netWorkSpace
ws = netWorkSpace('nws example')

# create a variable in the local R workspace that is linked to
# a netWorkSpace variable
nwsVariable(ws, 'x', 'single')

x <- 0
x <- 999  # overwrites the 0
x <- 3.14159  # overwrites the 999
x   # returns 3.14159
x   # returns 3.14159
x   # returns 3.14159

# create a 'fifo' mode variable
nwsVariable(ws, 'message', 'fifo')

message <- 1
message <- 2
message <- 3
message  # returns 1
message  # returns 2
message  # returns 3
  
## End(Not run)


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