Submission Method with Missing Arguments

Question

How can I avoid the classic error Error: argument "<argname>" is missing, with no default(see the example below) when I explicitly send the argument values ​​to subsequent S4 methods in this S4 method.

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Example

Large image

• Whe has a method foo()that calls the method bar().
• Both methods depend on xand y.
• The method of foo()sending the arguments xand yin bar()in an explicit way to: bar(x=x, y=y).

Now, the main thing is that I do not want to foo()care about whether any or all of the arguments passed along with are missing bar().

General methods

setGeneric(
    name="foo",
    signature=c("x", "y"),
    def=function(x, y, ...) {
        standardGeneric("foo")
    }
)
setGeneric(
    name="bar",
    signature=c("x", "y"),
    def=function(x, y, ...) {
        standardGeneric("bar")
    }
)

Methods for bar()

setMethod(
    f="bar", 
    signature=signature(x="missing", y="missing"), 
    definition=function(x, y, ...) {
        print("Doing what I'm supposed to do when both args are missing")
        return(NULL)
    }
)
setMethod(
    f="bar", 
    signature=signature(x="ANY", y="missing"), 
    definition=function(x, y, ...) {
        message("'y' is missing, but I can give you 'x':")
        print(x)
        return(NULL)
    }
)
setMethod(
    f="bar", 
    signature=signature(x="missing", y="ANY"), 
    definition=function(x, y, ...) {
        message("'x' is missing, but I can give you 'y':")
        print(y)
        return(NULL)
    }
)
setMethod(
    f="bar", 
    signature=signature(x="ANY", y="ANY"), 
    definition=function(x, y, ...) {
        message("x:")
        print(x)
        message("y:")
        print(y)
        return(NULL)
    }
)

Method for foo()

, , foo() , - , bar(). , bar() :

setMethod(
    f="foo", 
    signature=signature(x="ANY", y="ANY"), 
    definition=function(x, y, ...) {
        bar(x=x, y=y)    
    }
)

def , , x y:

> foo(x="Hello", y="World!")
x:
[1] "Hello"
y:
[1] "World!"
NULL
> foo(x="Hello")
Error in bar(x = x, y = y) : 
  error in evaluating the argument 'y' in selecting a method for function 'bar': Error: argument "y" is missing, with no default
> foo()
Error in bar(x = x, y = y) : 
  error in evaluating the argument 'x' in selecting a method for function 'bar': Error: argument "x" is missing, with no default

, :

setMethod(
    f="foo", 
    signature=signature(x="ANY", y="ANY"), 
    definition=function(x, y, ...) {
        if (missing(x) && missing(y)) {
            bar()    
        } else if (missing(x)) {
            bar(y=y)
        } else if (missing(y)) {
            bar(x=x)
        } else {
            bar(x=x, y=y)
        }
    }
)

> foo(x="Hello", y="World!")
x:
[1] "Hello"
y:
[1] "World!"
NULL
> foo(x="Hello")
'y' is missing, but I can give you 'x':
[1] "Hello"
NULL
> foo(y="World!")
'x' is missing, but I can give you 'y':
[1] "World!"
NULL
> foo()
[1] "Doing what I'm supposed to do when both args are missing"
NULL

, - if ... else. " if-else" bar(). , , , ? " ", .

NULL "" , missing() is.null() .

Answer 1

. ( " ", R.)

setMethod(
    f="foo", 
    signature=signature(x="ANY", y="ANY"), 
    definition=function(x, y, ...) {
        mc <- match.call()
        mc[[1]] <- quote(bar)
        eval(mc)
    }
)


foo(x="Hello")
# 'y' is missing, but I can give you 'x':
# [1] "Hello"
# NULL

foo(y="World")
# 'x' is missing, but I can give you 'y':
# [1] "World"
# NULL

foo()
# [1] "Doing what I'm supposed to do when both args are missing"
# NULL