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Create and name an object in one step

Source: R/bind.R
named-bind.Rd

Functions like new_class() and new_generic() take a name that, by convention, matches the name of the variable that you assign their result to. The := operator eliminates this duplication: Foo := new_class() is equivalent to Foo <- new_class(name = "Foo").

:= works with any function that has a name argument, but bear in mind that it adds name to the call as a named argument, so any other arguments supplied positionally will shift to fill the remaining parameters.

Usage

`:=`(lhs, rhs)

Arguments

lhs

A bare symbol: both the name of the variable to create and the name supplied to the right-hand side.

rhs

A call to a function with a name argument.

Value

The result of evaluating rhs, which is also assigned to lhs in the calling environment, returned invisibly.

Examples

Range := new_class(properties = list(
  start = class_double,
  end = class_double
))
Range
#> <Range> class
#> @ parent     : <S7_object>
#> @ constructor: function(start, end) {...}
#> @ validator  : <NULL>
#> @ properties :
#>  $ start: <double> = numeric(0)
#>  $ end: <double> = numeric(0)

describe := new_generic("x")
describe
#> <S7_generic> describe(x, ...) with 0 methods: