ianmcook commented on a change in pull request #10327:
URL: https://github.com/apache/arrow/pull/10327#discussion_r632797152
##########
File path: r/R/expression.R
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@@ -76,7 +76,15 @@
Expression <- R6Class("Expression", inherit = ArrowObject,
public = list(
ToString = function() compute___expr__ToString(self),
- type = function(schema) compute___expr__type(self, schema),
+ schema = NULL,
+ bind = function(schema) self$schema <- schema,
+ type = function() {
+ if (is.null(self$schema)) {
+ stop("Must bind() expression to a schema before returning its type",
call. = FALSE)
+ }
+ compute___expr__type(self, self$schema)
+ },
Review comment:
As you can see, calling the `$bind()` R6 method doesn't actually call
the `Bind()` C++ function; I attempted that at first but ran into some problems
so switched to doing it like this.
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