Custom delayed operations

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#127 opened on May 22, 2026 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 45/100

Issue type: Feature
Clarity: Mostly clear
Activity status: Quiet
Tech stack: r
Domain: data

Research direction

Start by reading the showtree and .rec_showtree methods, then trace how getArrayElement handles DelayedOp subclasses. Reproduce the example with DelayedAffineSeed and DelayedTranslateSeed, including the subset operation on the temporary Zarr array. Done means external classes containing DelayedOp can participate in the requested delayed-operation inspection or access flow without the reported missing-method error.

Written by the indexing model from the issue text.

Description

Dear @hpages,

I am working on devising lazy image transformations for https://github.com/HelenaLC/SpatialData/issues/162.

I was wondering if it is possible to use showtree or .rec_showtree methods (or similar methods) for external classes that facilitate delayed operations.

I have tried below, but it requires me to define additional methods for these classes that contain DelayedOp:

setClass(
  "DelayedAffineSeed",
  contains = "DelayedOp",
  slots = c(
    seed = "ANY",
    dim = "integer",
    dimnames = "list",
    m = "matrix",
    axes = "character",
    filter = "character",
    bg.col = "character",
    antialias = "logical",
    trace = "logical"
  )
)

setClass(
  "DelayedTranslateSeed",
  contains = "DelayedOp",
  slots = c(
    seed = "ANY",
    dim = "integer",
    dimnames = "list",
    shift = "numeric",
    axes = "character"
  )
)

# save as zarr
td <- tempfile(fileext = ".zarr")
delayed_img <- writeZarrArray(x = EBImage::imageData(img), zarr_path = td) 

# affine
rotated_delayed_img <- lazy_affine(delayed_img, m = m, filter = "bilinear")

# translate
translate_delayed_img <- lazy_translate(rotated_delayed_img, shift = c(100,200))

# subset
subset_delayed_img <- translate_delayed_img[100:200, 100:200]

> subset_delayed_img@seed
101x101 double: Subset
└─ 1024x512 double: DelayedTranslateSeed object
Error: unable to find an inherited method for function ‘getArrayElement’ for signature ‘x = "DelayedTranslateSeed"’

Dominant language: R
Stars: 29
Forks: 12
PR merge metrics: No merged PRs in 30d

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