Funções auxiliares

Este tópico contém várias funções auxiliares comumente usadas em extensões M. Essas funções podem eventualmente ser movidas para a biblioteca M oficial, mas, por enquanto, podem ser copiadas em seu código de arquivo de extensão. Você não deve marcar nenhuma dessas funções como dentro shared do código de extensão.

Table.ToNavigationTable

Essa função adiciona os metadados de tipo de tabela necessários para que sua extensão retorne um valor de tabela que Power Query possa reconhecer como uma Árvore de Navegação. Consulte Tabelas de navegação para obter mais informações.

Table.ToNavigationTable = (
    table as table,
    keyColumns as list,
    nameColumn as text,
    dataColumn as text,
    itemKindColumn as text,
    itemNameColumn as text,
    isLeafColumn as text
) as table =>
    let
        tableType = Value.Type(table),
        newTableType = Type.AddTableKey(tableType, keyColumns, true) meta 
        [
            NavigationTable.NameColumn = nameColumn, 
            NavigationTable.DataColumn = dataColumn,
            NavigationTable.ItemKindColumn = itemKindColumn, 
            Preview.DelayColumn = itemNameColumn, 
            NavigationTable.IsLeafColumn = isLeafColumn
        ],
        navigationTable = Value.ReplaceType(table, newTableType)
    in
        navigationTable;
Parâmetro Detalhes
tabela Sua tabela de navegação.
Keycolumns Lista de nomes de coluna que atuam como a chave primária para sua tabela de navegação.
Namecolumn O nome da coluna que deve ser usada como o nome de exibição no navegador.
Datacolumn O nome da coluna que contém a Tabela ou Função a ser exibida.
itemKindColumn O nome da coluna a ser usada para determinar o tipo de ícone a ser exibido. Os valores válidos para a coluna Table são e Function .
itemNameColumn O nome da coluna a ser usada para determinar o tipo de dica de ferramenta a ser exibida. Os valores válidos para a coluna Table são e Function .
isLeafColumn O nome da coluna usada para determinar se este é um nó folha ou se o nó pode ser expandido para conter outra tabela de navegação.

Exemplo de uso:

shared MyExtension.Contents = () =>
    let
        objects = #table(
            {"Name",       "Key",        "Data",                           "ItemKind", "ItemName", "IsLeaf"},{
            {"Item1",      "item1",      #table({"Column1"}, {{"Item1"}}), "Table",    "Table",    true},
            {"Item2",      "item2",      #table({"Column1"}, {{"Item2"}}), "Table",    "Table",    true},
            {"Item3",      "item3",      FunctionCallThatReturnsATable(),  "Table",    "Table",    true},            
            {"MyFunction", "myfunction", AnotherFunction.Contents(),       "Function", "Function", true}
            }),
        NavTable = Table.ToNavigationTable(objects, {"Key"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf")
    in
        NavTable;

Manipulação de URI

Uri.FromParts

Essa função constrói uma URL completa com base em campos individuais no registro. Ele atua como o inverso de Uri.Parts.

Uri.FromParts = (parts) =>
    let
        port = if (parts[Scheme] = "https" and parts[Port] = 443) or (parts[Scheme] = "http" and parts[Port] = 80) then "" else ":" & Text.From(parts[Port]),
        div1 = if Record.FieldCount(parts[Query]) > 0 then "?" else "",
        div2 = if Text.Length(parts[Fragment]) > 0 then "#" else "",
        uri = Text.Combine({parts[Scheme], "://", parts[Host], port, parts[Path], div1, Uri.BuildQueryString(parts[Query]), div2, parts[Fragment]})
    in
        uri;

Uri.GetHost

Essa função retorna o esquema, o host e a porta padrão (para HTTP/HTTPS) para uma determinada URL. Por exemplo, https://bing.com/subpath/query?param=1&param2=hello se tornaria https://bing.com:443.

Isso é particularmente útil para a criação de ResourcePath .

Uri.GetHost = (url) =>
    let
        parts = Uri.Parts(url),
        port = if (parts[Scheme] = "https" and parts[Port] = 443) or (parts[Scheme] = "http" and parts[Port] = 80) then "" else ":" & Text.From(parts[Port])
    in
        parts[Scheme] & "://" & parts[Host] & port;

ValidateUrlScheme

Essa função verifica se o usuário entrou em uma URL HTTPS e gera um erro se não tiver. Isso é necessário para URLs inseridas pelo usuário para conectores certificados.

ValidateUrlScheme = (url as text) as text => if (Uri.Parts(url)[Scheme] <> "https") then error "Url scheme must be HTTPS" else url;

Para aplicá-lo, basta envolver o url parâmetro em sua função de acesso a dados.

DataAccessFunction = (url as text) as table =>
    let
        _url = ValidateUrlScheme(url),
        source = Web.Contents(_url)
    in
        source;

Recuperando dados

Value.WaitFor

Essa função é útil ao fazer uma solicitação HTTP assíncrona e você precisa sondar o servidor até que a solicitação seja concluída.

Value.WaitFor = (producer as function, interval as function, optional count as number) as any =>
    let
        list = List.Generate(
            () => {0, null},
            (state) => state{0} <> null and (count = null or state{0} < count),
            (state) => if state{1} <> null then {null, state{1}} else {1 + state{0}, Function.InvokeAfter(() => producer(state{0}), interval(state{0}))},
            (state) => state{1})
    in
        List.Last(list);

Table.GenerateByPage

Essa função é usada quando uma API retorna dados em um formato incremental/pa pa por página, o que é comum para muitas APIs REST. O argumento é uma função que aceita um único parâmetro, que será o resultado da chamada getNextPage anterior para e deve retornar um getNextPage nullable table .

getNextPage = (lastPage) as nullable table => ...`

getNextPage é chamado repetidamente até retornar null . A função vai collar todas as páginas em uma única tabela. Quando o resultado da primeira chamada para getNextPage é nulo, uma tabela vazia é retornada.

// The getNextPage function takes a single argument and is expected to return a nullable table
Table.GenerateByPage = (getNextPage as function) as table =>
    let        
        listOfPages = List.Generate(
            () => getNextPage(null),            // get the first page of data
            (lastPage) => lastPage <> null,     // stop when the function returns null
            (lastPage) => getNextPage(lastPage) // pass the previous page to the next function call
        ),
        // concatenate the pages together
        tableOfPages = Table.FromList(listOfPages, Splitter.SplitByNothing(), {"Column1"}),
        firstRow = tableOfPages{0}?
    in
        // if we didn't get back any pages of data, return an empty table
        // otherwise set the table type based on the columns of the first page
        if (firstRow = null) then
            Table.FromRows({})
        else        
            Value.ReplaceType(
                Table.ExpandTableColumn(tableOfPages, "Column1", Table.ColumnNames(firstRow[Column1])),
                Value.Type(firstRow[Column1])
            );

Observações adicionais:

  • A função precisará recuperar a URL da próxima página (ou o número da página ou quaisquer outros valores usados getNextPage para implementar a lógica de paging). Isso geralmente é feito adicionando meta valores à página antes de reavolvê-la.
  • As colunas e o tipo de tabela da tabela combinada (ou seja, todas as páginas juntas) são derivados da primeira página de dados. A getNextPage função deve normalizar cada página de dados.
  • A primeira chamada para getNextPage recebe um parâmetro nulo.
  • getNextPage deve retornar nulo quando não houver mais páginas.

Um exemplo de como usar essa função pode ser encontrado no exemplo do Githube no exemplo de paging tripPin.

Github.PagedTable = (url as text) => Table.GenerateByPage((previous) =>
    let
        // If we have a previous page, get its Next link from metadata on the page.
        next = if (previous <> null) then Value.Metadata(previous)[Next] else null,
        // If we have a next link, use it, otherwise use the original URL that was passed in.
        urlToUse = if (next <> null) then next else url,
        // If we have a previous page, but don't have a next link, then we're done paging.
        // Otherwise retrieve the next page.
        current = if (previous <> null and next = null) then null else Github.Contents(urlToUse),
        // If we got data back from the current page, get the link for the next page
        link = if (current <> null) then Value.Metadata(current)[Next] else null
    in
        current meta [Next=link]);

SchemaTransformTable

EnforceSchema.Strict = 1;               // Add any missing columns, remove extra columns, set table type
EnforceSchema.IgnoreExtraColumns = 2;   // Add missing columns, do not remove extra columns
EnforceSchema.IgnoreMissingColumns = 3; // Do not add or remove columns

SchemaTransformTable = (table as table, schema as table, optional enforceSchema as number) as table =>
    let
        // Default to EnforceSchema.Strict
        _enforceSchema = if (enforceSchema <> null) then enforceSchema else EnforceSchema.Strict,

        // Applies type transforms to a given table
        EnforceTypes = (table as table, schema as table) as table =>
            let
                map = (t) => if Type.Is(t, type list) or Type.Is(t, type record) or t = type any then null else t,
                mapped = Table.TransformColumns(schema, {"Type", map}),
                omitted = Table.SelectRows(mapped, each [Type] <> null),
                existingColumns = Table.ColumnNames(table),
                removeMissing = Table.SelectRows(omitted, each List.Contains(existingColumns, [Name])),
                primativeTransforms = Table.ToRows(removeMissing),
                changedPrimatives = Table.TransformColumnTypes(table, primativeTransforms)
            in
                changedPrimatives,

        // Returns the table type for a given schema
        SchemaToTableType = (schema as table) as type =>
            let
                toList = List.Transform(schema[Type], (t) => [Type=t, Optional=false]),
                toRecord = Record.FromList(toList, schema[Name]),
                toType = Type.ForRecord(toRecord, false)
            in
                type table (toType),

        // Determine if we have extra/missing columns.
        // The enforceSchema parameter determines what we do about them.
        schemaNames = schema[Name],
        foundNames = Table.ColumnNames(table),
        addNames = List.RemoveItems(schemaNames, foundNames),
        extraNames = List.RemoveItems(foundNames, schemaNames),
        tmp = Text.NewGuid(),
        added = Table.AddColumn(table, tmp, each []),
        expanded = Table.ExpandRecordColumn(added, tmp, addNames),
        result = if List.IsEmpty(addNames) then table else expanded,
        fullList =
            if (_enforceSchema = EnforceSchema.Strict) then
                schemaNames
            else if (_enforceSchema = EnforceSchema.IgnoreMissingColumns) then
                foundNames
            else
                schemaNames & extraNames,

        // Select the final list of columns.
        // These will be ordered according to the schema table.
        reordered = Table.SelectColumns(result, fullList, MissingField.Ignore),
        enforcedTypes = EnforceTypes(reordered, schema),
        withType = if (_enforceSchema = EnforceSchema.Strict) then Value.ReplaceType(enforcedTypes, SchemaToTableType(schema)) else enforcedTypes
    in
        withType;

Table.ChangeType

let
    // table should be an actual Table.Type, or a List.Type of Records
    Table.ChangeType = (table, tableType as type) as nullable table =>
        // we only operate on table types
        if (not Type.Is(tableType, type table)) then error "type argument should be a table type" else
        // if we have a null value, just return it
        if (table = null) then table else
        let
            columnsForType = Type.RecordFields(Type.TableRow(tableType)),
            columnsAsTable = Record.ToTable(columnsForType),
            schema = Table.ExpandRecordColumn(columnsAsTable, "Value", {"Type"}, {"Type"}),
            previousMeta = Value.Metadata(tableType),

            // make sure we have a table
            parameterType = Value.Type(table),
            _table =
                if (Type.Is(parameterType, type table)) then table
                else if (Type.Is(parameterType, type list)) then
                    let
                        asTable = Table.FromList(table, Splitter.SplitByNothing(), {"Column1"}),
                        firstValueType = Value.Type(Table.FirstValue(asTable, null)),
                        result =
                            // if the member is a record (as expected), then expand it. 
                            if (Type.Is(firstValueType, type record)) then
                                Table.ExpandRecordColumn(asTable, "Column1", schema[Name])
                            else
                                error Error.Record("Error.Parameter", "table argument is a list, but not a list of records", [ ValueType = firstValueType ])
                    in
                        if (List.IsEmpty(table)) then
                            #table({"a"}, {})
                        else result
                else
                    error Error.Record("Error.Parameter", "table argument should be a table or list of records", [ValueType = parameterType]),

            reordered = Table.SelectColumns(_table, schema[Name], MissingField.UseNull),

            // process primitive values - this will call Table.TransformColumnTypes
            map = (t) => if Type.Is(t, type table) or Type.Is(t, type list) or Type.Is(t, type record) or t = type any then null else t,        
            mapped = Table.TransformColumns(schema, {"Type", map}),
            omitted = Table.SelectRows(mapped, each [Type] <> null),
            existingColumns = Table.ColumnNames(reordered),
            removeMissing = Table.SelectRows(omitted, each List.Contains(existingColumns, [Name])),
            primativeTransforms = Table.ToRows(removeMissing),
            changedPrimatives = Table.TransformColumnTypes(reordered, primativeTransforms),
        
            // Get the list of transforms we'll use for Record types
            recordColumns = Table.SelectRows(schema, each Type.Is([Type], type record)),
            recordTypeTransformations = Table.AddColumn(recordColumns, "RecordTransformations", each (r) => Record.ChangeType(r, [Type]), type function),
            recordChanges = Table.ToRows(Table.SelectColumns(recordTypeTransformations, {"Name", "RecordTransformations"})),

            // Get the list of transforms we'll use for List types
            listColumns = Table.SelectRows(schema, each Type.Is([Type], type list)),
            listTransforms = Table.AddColumn(listColumns, "ListTransformations", each (t) => List.ChangeType(t, [Type]), Function.Type),
            listChanges = Table.ToRows(Table.SelectColumns(listTransforms, {"Name", "ListTransformations"})),

            // Get the list of transforms we'll use for Table types
            tableColumns = Table.SelectRows(schema, each Type.Is([Type], type table)),
            tableTransforms = Table.AddColumn(tableColumns, "TableTransformations", each (t) => @Table.ChangeType(t, [Type]), Function.Type),
            tableChanges = Table.ToRows(Table.SelectColumns(tableTransforms, {"Name", "TableTransformations"})),

            // Perform all of our transformations
            allColumnTransforms = recordChanges & listChanges & tableChanges,
            changedRecordTypes = if (List.IsEmpty(allColumnTransforms)) then changedPrimatives else Table.TransformColumns(changedPrimatives, allColumnTransforms, null, MissingField.Ignore),

            // set final type
            withType = Value.ReplaceType(changedRecordTypes, tableType)
        in
            if (List.IsEmpty(Record.FieldNames(columnsForType))) then table else withType meta previousMeta,

    // If given a generic record type (no predefined fields), the original record is returned
    Record.ChangeType = (record as record, recordType as type) =>
        let
            // record field format is [ fieldName = [ Type = type, Optional = logical], ... ]
            fields = try Type.RecordFields(recordType) otherwise error "Record.ChangeType: failed to get record fields. Is this a record type?",
            fieldNames = Record.FieldNames(fields),
            fieldTable = Record.ToTable(fields),
            optionalFields = Table.SelectRows(fieldTable, each [Value][Optional])[Name],
            requiredFields = List.Difference(fieldNames, optionalFields),
            // make sure all required fields exist
            withRequired = Record.SelectFields(record, requiredFields, MissingField.UseNull),
            // append optional fields
            withOptional = withRequired & Record.SelectFields(record, optionalFields, MissingField.Ignore),
            // set types
            transforms = GetTransformsForType(recordType),
            withTypes = Record.TransformFields(withOptional, transforms, MissingField.Ignore),
            // order the same as the record type
            reorder = Record.ReorderFields(withTypes, fieldNames, MissingField.Ignore)
        in
            if (List.IsEmpty(fieldNames)) then record else reorder,

    List.ChangeType = (list as list, listType as type) =>
        if (not Type.Is(listType, type list)) then error "type argument should be a list type" else
        let
            listItemType = Type.ListItem(listType),
            transform = GetTransformByType(listItemType),
            modifiedValues = List.Transform(list, transform),
            typed = Value.ReplaceType(modifiedValues, listType)
        in
            typed,

    // Returns a table type for the provided schema table
    Schema.ToTableType = (schema as table) as type =>
        let
            toList = List.Transform(schema[Type], (t) => [Type=t, Optional=false]),
            toRecord = Record.FromList(toList, schema[Name]),
            toType = Type.ForRecord(toRecord, false),
            previousMeta = Value.Metadata(schema)
        in
            type table (toType) meta previousMeta,

    // Returns a list of transformations that can be passed to Table.TransformColumns, or Record.TransformFields
    // Format: {"Column", (f) => ...) .... ex: {"A", Number.From}
    GetTransformsForType = (_type as type) as list =>
        let
            fieldsOrColumns = if (Type.Is(_type, type record)) then Type.RecordFields(_type)
                            else if (Type.Is(_type, type table)) then Type.RecordFields(Type.TableRow(_type))
                            else error "GetTransformsForType: record or table type expected",
            toTable = Record.ToTable(fieldsOrColumns),
            transformColumn = Table.AddColumn(toTable, "Transform", each GetTransformByType([Value][Type]), Function.Type),
            transformMap = Table.ToRows(Table.SelectColumns(transformColumn, {"Name", "Transform"}))
        in
            transformMap,

    GetTransformByType = (_type as type) as function =>
                if (Type.Is(_type, type number)) then Number.From
        else if (Type.Is(_type, type text)) then Text.From
        else if (Type.Is(_type, type date)) then Date.From
        else if (Type.Is(_type, type datetime)) then DateTime.From
        else if (Type.Is(_type, type duration)) then Duration.From
        else if (Type.Is(_type, type datetimezone)) then DateTimeZone.From
        else if (Type.Is(_type, type logical)) then Logical.From
        else if (Type.Is(_type, type time)) then Time.From
        else if (Type.Is(_type, type record)) then (t) => if (t <> null) then @Record.ChangeType(t, _type) else t
        else if (Type.Is(_type, type table)) then (t) => if (t <> null) then @Table.ChangeType(t, _type) else t
        else if (Type.Is(_type, type list)) then (t) => if (t <> null) then @List.ChangeType(t, _type) else t
        else (t) => t
in
    Table.ChangeType