Created
January 3, 2019 13:39
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| collector = function(df) { | |
| if (!is.data.frame(df)) stop("df must be data.frame") | |
| structure(list(df=df, accessed=list()), class = "collector") | |
| } | |
| `[[.collector` = function(c, attr, ...) { | |
| c$accessed = c(c$accessed, attr) | |
| c$df[[attr]] | |
| } | |
| c = collector(data_frame(a=1)) | |
| c[['a']] | |
| c$accessed # -> list() != list('a') WHY!? |
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