189 - Add Pattern Matching Callbacks for Dash R #228
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| # Simple Example with ALL | ||
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There was a problem hiding this comment. Nice sample app! As far as tests go, I imagine we might want to consider
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| library(dash) | ||
| library(dashCoreComponents) | ||
| library(dashHtmlComponents) | ||
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| app <- Dash$new() | ||
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| app$layout(htmlDiv(list( | ||
| htmlButton("Add Filter", id="add-filter", n_clicks=0), | ||
| htmlDiv(id="dropdown-container", children=list()), | ||
| htmlDiv(id="dropdown-container-output"), | ||
| dccInput(id='my-id', value='initial value', type='text'), | ||
| htmlDiv(id='my-div') | ||
| ))) | ||
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| app$callback( | ||
| output(id="dropdown-container", property = "children"), | ||
| params = list( | ||
| input(id = "add-filter", property = "n_clicks"), | ||
| state(id = "dropdown-container", property = "children") | ||
| ), | ||
| display_dropdowns <- function(n_clicks, children){ | ||
| new_dropdown = dccDropdown( | ||
| id=list( | ||
| "index" = n_clicks, | ||
| "type" = "filter-dropdown" | ||
| ), | ||
| options = lapply(1:4, function(x){ | ||
| list("label" = x, "value" = x) | ||
| }) | ||
| ) | ||
| children[[n_clicks + 1]] <- new_dropdown | ||
| return(children) | ||
| } | ||
| ) | ||
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| app$callback( | ||
| output(id="dropdown-container-output", property="children"), | ||
| params = list( | ||
| input(id=list("index" = "ALL", "type" = "filter-dropdown"), property= "value") | ||
| ), | ||
| display_output <- function(test){ | ||
| print(test) | ||
| return(htmlDiv( | ||
| lapply(1:length(test), function(x){ | ||
| return(htmlDiv(sprintf("Dropdown %s = %s", x, test[[x]]))) | ||
| }) | ||
| )) | ||
| } | ||
| ) | ||
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| app$callback( | ||
| output=list(id='my-div', property='children'), | ||
| params=list(input(id='my-id', property='value')), | ||
| function(input_value) { | ||
| sprintf("You've entered \"%s\"", input_value) | ||
| }) | ||
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| app$run_server(debug=F, showcase = TRUE) | ||
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| # Standard Callback Example | ||
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| library(dash) | ||
| library(dashCoreComponents) | ||
| library(dashHtmlComponents) | ||
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| app <- Dash$new() | ||
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| app$layout( | ||
| htmlDiv( | ||
| list( | ||
| dccInput(id='my-id', value='initial value', type='text'), | ||
| htmlDiv(id='my-div') | ||
| ) | ||
| ) | ||
| ) | ||
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| app$callback( | ||
| output=list(id='my-div', property='children'), | ||
| params=list(input(id='my-id', property='value')), | ||
| function(input_value) { | ||
| sprintf("You've entered \"%s\"", input_value) | ||
| }) | ||
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| app$run_server() | ||
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| # Simple Example with MATCH | ||
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| library(dash) | ||
| library(dashCoreComponents) | ||
| library(dashHtmlComponents) | ||
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| app <- Dash$new() | ||
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| app$layout(htmlDiv(list( | ||
| htmlButton("Add Filter", id="dynamic-add-filter", n_clicks=0), | ||
| htmlDiv(id="dynamic-dropdown-container", children=list()) | ||
| ))) | ||
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| app$callback( | ||
| output(id="dynamic-dropdown-container", "children"), | ||
| params = list( | ||
| input("dynamic-add-filter", "n_clicks"), | ||
| state("dynamic-dropdown-container", "children") | ||
| ), | ||
| display_dropdown <- function(n_clicks, children){ | ||
| new_element = htmlDiv(list( | ||
| dccDropdown( | ||
| id = list("type" = "dynamic-dropdown", "index" = sprintf("%s", n_clicks)), | ||
| options = lapply(c("NYC", "MTL", "LA", "TOKYO"), function(x){ | ||
| list("label" = x, "value" = x) | ||
| }) | ||
| ), | ||
| htmlDiv( | ||
| id = list("type" = "dynamic-output", "index" = sprintf("%s", n_clicks)) | ||
| ) | ||
| )) | ||
| children <- c(children, list(new_element)) | ||
| return(children) | ||
| } | ||
| ) | ||
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| app$callback( | ||
| output(list("type" = "dynamic-output", "index" = "MATCH"), "children"), | ||
| params = list( | ||
| input(list("type" = "dynamic-dropdown", "index" = "MATCH"), "value"), | ||
| state(list("type" = "dynamic-dropdown", "index" = "MATCH"), "id") | ||
| ), | ||
| display_output <- function(value, id){ | ||
| print(id) | ||
| print(value) | ||
| return(htmlDiv(list( | ||
| id, value | ||
| ))) | ||
| } | ||
| ) | ||
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| app$run_server(showcase = T, debug = F) | ||
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We could 🌴 this up a little by moving the
unlist(input_element)outside of theif.If what we're mostly interested in is
names(unlisted_input), we could actually assign that instead, and use it where needed below.Just an observation, but I think this may be a circumstance where using a
forloop and a conditional causes a lot of housekeeping that could avoided by retaining the originalliststructure. For example, here:we have to call☺️
namestwice, even though we already extracted the names aboveOn the other hand, had we left it as a
list, we could instead trywhich I think would give us what we want in a slightly easier-to-read/easier-to-follow way. I haven't tried it (and
input_listis so compact it hardly matters), but I suspect this might be a bit more efficient for large lists as well.Uh oh!
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I'm a bit hesitant to change this part for a couple of reasons. For a normal callback,
request$body$inputsis already a named list, and unlisting that would make handling regular callbacks more complicated as we then have to append a list of lists tocallback_argsfor default callbacks.In the case of pattern matching callbacks, each
input_elementis a list of lists. By unlisting it we can access each of the wildcard inputs. I tried to use a vector to subset as you suggested, but while it works for some scenarios, on the initial call of the PMC we run into a subscript out of bounds error, and it might overcomplicate it to account for another condition. We'll also have to deal withNAvalues that can come up if the input doesn't have avalue.index.I'll try to figure out a way to simplify it and improve readability, but I think unlisting with a
for loopin this case would have to be a necessary evil.There was a problem hiding this comment.
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OK, trust your judgment (since I do as well). Though one remark I'd make is that the out of bounds error may be related to the current default values for callback inputs, which is
list(NULL). In that case, we could probably just ensure these values are handled properly, but don't worry about this for now.We can always revisit the implementation later if we have an epiphany about making it a little more concise, for the moment it looks OK as-is.