Merge pull request #144 from plotly/helper_functions

Helper functions

Author: waralex

Project.toml

@@ -4,6 +4,7 @@ authors = ["Chris Parmer <chris@plotly.com>", "Alexandr Romanenko <waralex@gmail
 version = "1.0.0"
 
 [deps]
+Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
 CodecZlib = "944b1d66-785c-5afd-91f1-9de20f533193"
 DashBase = "03207cf0-e2b3-4b91-9ca8-690cf0fb507e"
 DashCoreComponents = "1b08a953-4be3-4667-9a23-9da06441d987"

src/Dash.jl

@@ -26,6 +26,7 @@ include("resources/application.jl")
 include("handlers.jl")
 include("server.jl")
 include("init.jl")
+include("components_utils/_components_utils.jl")
 include("plotly_base.jl")
 
 @doc """

src/components_utils/_components_utils.jl

@@ -0,0 +1,2 @@
+include("express.jl")
+include("table_format.jl")

src/components_utils/express.jl

@@ -0,0 +1,102 @@
+import Base64
+export dcc_send_file, dcc_send_string, dcc_send_bytes
+"""
+    dbc_send_file(path::AbstractString, filename = nothing; type = nothing)
+
+Convert a file into the format expected by the Download component.
+
+# Arguments
+- `path` - path to the file to be sent
+- `filename` - name of the file, if not provided the original filename is used
+- `type` - type of the file (optional, passed to Blob in the javascript layer)
+"""
+function dcc_send_file(path, filename = nothing; type = nothing)
+    filename = isnothing(filename) ? basename(path) : filename
+    return dcc_send_bytes(read(path), filename, type = type)
+end
+
+"""
+    dcc_send_bytes(src::AbstractVector{UInt8}, filename; type = nothing)
+    dcc_send_bytes(writer::Function, data, filename; type = nothing)
+
+Convert vector of bytes into the format expected by the Download component.
+`writer` function must have signature `(io::IO, data)`
+
+# Examples
+
+Sending binary content
+```julia
+file_data = read("path/to/file")
+callback!(app, Output("download", "data"), Input("download-btn", "n_clicks"), prevent_initial_call = true) do n_clicks
+    return dcc_send_bytes(file_data, "filename.fl")
+end
+```
+
+Sending `DataFrame` in `Arrow` format
+```julia
+using DataFrames, Arrow
+...
+df = DataFrame(...)
+callback!(app, Output("download", "data"), Input("download-btn", "n_clicks"), prevent_initial_call = true) do n_clicks
+    return dcc_send_bytes(Arrow.write, df, "df.arr")
+end
+```
+"""
+function dcc_send_bytes(src::AbstractVector{UInt8}, filename; type = nothing)
+
+    return Dict(
+        :content => Base64.base64encode(src),
+        :filename => filename,
+        :type => type,
+        :base64 => true
+    )
+end
+
+function dcc_send_bytes(writer::Function, data, filename; type = nothing)
+    io = IOBuffer()
+    writer(io, data)
+    return dcc_send_bytes(take!(io), filename, type = type)
+end
+
+"""
+    dcc_send_data(src::AbstractString, filename; type = nothing)
+    dcc_send_data(writer::Function, data, filename; type = nothing)
+
+Convert string into the format expected by the Download component.
+`writer` function must have signature `(io::IO, data)`
+
+# Examples
+
+Sending string content
+```julia
+text_data = "this is the test"
+callback!(app, Output("download", "data"), Input("download-btn", "n_clicks"), prevent_initial_call = true) do n_clicks
+    return dcc_send_string(text_data, "text.txt")
+end
+```
+
+Sending `DataFrame` in `CSV` format
+```julia
+using DataFrames, CSV
+...
+df = DataFrame(...)
+callback!(app, Output("download", "data"), Input("download-btn", "n_clicks"), prevent_initial_call = true) do n_clicks
+    return dcc_send_string(CSV.write, df, "df.csv")
+end
+```
+"""
+function dcc_send_string(src::AbstractString, filename; type = nothing)
+
+    return Dict(
+        :content => src,
+        :filename => filename,
+        :type => type,
+        :base64 => false
+    )
+end
+
+function dcc_send_string(writer::Function, data, filename; type = nothing)
+    io = IOBuffer()
+    writer(io, data)
+    return dcc_send_string(String(take!(io)), filename, type = type)
+end