Clear fields that are defined to have cached values

Clear fields that are defined to have cached values by assigning NULL to these fields.

# S3 method for class 'Object'
clearCache(this, recursive=TRUE, gc=FALSE, ...)

Arguments

recursive

If TRUE, the same method is called also on all fields that are Object:s. Circular dependencies can exists.

gc

If TRUE, the garbage collector is called, otherwise not.

...

Not used.

Value

Returns itself (invisible).

Author

Henrik Bengtsson

See also

For more information see Object.

Examples

# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Defining a class with a 'cached' fields
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
setConstructorS3("CachedObject", function(...) {
  extend(Object(), "CachedObject",
    ...
  )
})

setMethodS3("as.character", "CachedObject", function(this, ...) {
  s <- NextMethod("as.character", this, ...)
  s <- sprintf("%s RAM: %.2fkb.", s, objectSize(this)/1024)
  s
})
#> NULL


# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Example of clearing a cache fields, reassigning it,
# and then clearing it again
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
obj <- CachedObject(a=1, b=1:10^5, "cached:c"=1:10^6)
print(obj)
#> [1] "CachedObject: 0x600f7acc5d80"
print(ll(obj))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      b    numeric    100000     400048
#> 3      c    numeric   1000000    4000048

clearCache(obj, gc=TRUE)
print(obj)
#> [1] "CachedObject: 0x600f7acc5d80"
print(ll(obj))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      b    numeric    100000     400048
#> 3      c       NULL         0          0


obj$c <- 1:10^6
#> Error in getStaticInstance.Object(this): Cannot get static instance. Failed to locate Class object for class 'CachedObject'.
print(obj)
#> [1] "CachedObject: 0x600f7acc5d80"
print(ll(obj))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      b    numeric    100000     400048
#> 3      c       NULL         0          0

clearCache(obj, gc=TRUE)
print(obj)
#> [1] "CachedObject: 0x600f7acc5d80"
print(ll(obj))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      b    numeric    100000     400048
#> 3      c       NULL         0          0


# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Clearing cached fields recursively and make sure it
# avoids race conditions due to circular dependences
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
objA <- CachedObject(a=2, "cached:c"=1:10^6, prev=NULL)
print(ll(objA))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      c    numeric   1000000    4000048
#> 3   prev       NULL         0          0

objB <- CachedObject(a=2, "cached:c"=1:10^6, prev=objA)
print(ll(objB))
#>   member   data.class dimension objectSize
#> 1      a      numeric         1         56
#> 2      c      numeric   1000000    4000048
#> 3   prev CachedObject         1    4000552

objC <- CachedObject(a=3, "cached:c"=1:10^6, prev=objB)
print(ll(objC))
#>   member   data.class dimension objectSize
#> 1      a      numeric         1         56
#> 2      c      numeric   1000000    4000048
#> 3   prev CachedObject         1    4001072

objA$prev <- objC
#> Error in getStaticInstance.Object(this): Cannot get static instance. Failed to locate Class object for class 'CachedObject'.

clearCache(objA, gc=TRUE)
print(ll(objA))
#>   member data.class dimension objectSize
#> 1      a    numeric         1         56
#> 2      c       NULL         0          0
#> 3   prev       NULL         0          0
print(ll(objB))
#>   member   data.class dimension objectSize
#> 1      a      numeric         1         56
#> 2      c      numeric   1000000    4000048
#> 3   prev CachedObject         1        504
print(ll(objC))
#>   member   data.class dimension objectSize
#> 1      a      numeric         1         56
#> 2      c      numeric   1000000    4000048
#> 3   prev CachedObject         1    4001072