Read content from the connector — read

Generic implementing of how to read content from the different connector objects:

ConnectorDBI: Uses DBI::dbReadTable() to read the table from the DBI connection.

ConnectorFS: Uses read_file() to read a given file. The underlying function used, and thereby also the arguments available through ... depends on the file extension.

Usage

read_cnt(connector_object, name, ...)

# S3 method for class 'ConnectorDBI'
read_cnt(connector_object, name, ...)

# S3 method for class 'ConnectorFS'
read_cnt(connector_object, name, ...)

Arguments

connector_object: Connector The connector object to use.
name: character Name of the content to read, write, or remove. Typically the table name.
...: Additional arguments passed to the method for the individual connector.

Value

R object with the content. For rectangular data a data.frame.

Examples

# Read table from DBI database
cnt <- connector_dbi(RSQLite::SQLite())

cnt |>
  write_cnt(iris, "iris")

cnt |>
  list_content_cnt()
#> [1] "iris"

cnt |>
  read_cnt("iris") |>
  head()
#>   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1          5.1         3.5          1.4         0.2  setosa
#> 2          4.9         3.0          1.4         0.2  setosa
#> 3          4.7         3.2          1.3         0.2  setosa
#> 4          4.6         3.1          1.5         0.2  setosa
#> 5          5.0         3.6          1.4         0.2  setosa
#> 6          5.4         3.9          1.7         0.4  setosa

# Write and read a CSV file using the file storage connector

folder <- withr::local_tempdir()
cnt <- connector_fs(folder)

cnt |>
  write_cnt(iris, "iris.csv")
#> Error: Cannot open file for writing:
#> * '/tmp/RtmppxiTmW/file1fc04bc56a7d/iris.csv'

cnt |>
  read_cnt("iris.csv") |>
  head()
#> Error in find_file(name, root = connector_object$path): No file found or multiple files found with the same name