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艾菲尔:do_all或do_if有没有一种方法可以在一个集合中搜索一个元素而不必编写整个特性?

eiffel

0

Pipo · 技术社区 · 6 年前

across
    collection as l_item
until 
    Result /= Void
loop
    if l_item.item.name.is_equal ("foo") then
        Result := l_item.item
    end
end

collection.do_if (agent ...)

使用示例可以是:

search_item_with_id (an_id: INTEGER)
        -- Moves items cursor if not found is_after
    local
        l_found: BOOLEAN
    do
        from
            items.start
        until
            items.after or l_found
        loop
            l_found := items.item.primary_key = an_id
            if not l_found then
                items.forth
            end
        end
    ensure
        cursor_on_element_if_found: not items.after implies items.item.primary_key = an_id
    end

1 回复 | 直到 6 年前

1

javierv 6 年前

是,请检查以下示例,并使用 do_all 和 do_if 使用 inline agents

查课 LINEAR 在里面 base

Collection.do_all (action: PROCEDURE [G]) :应用 action

Collection.do_if (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) :应用每一项都满足 test

class
    AGENTS_EXAMPLE

create
    make

feature

    make
        do
            print ("%NDo ALL examples: %N")
            example_do_all_with_inline
            example_do_all_with_feature
            print ("%NDo if examples: %N")
            example_do_if_with_inline
            example_do_if_with_features
        end

feature -- Access

    languages: ARRAY [STRING]
            -- Programming languages
        once
            Result := <<"Eiffel", "Ruby", "Python", "C++", "Perl", "Java", "Go", "Rust">>
        end

feature -- Access DO-ALL

    example_do_all_with_inline
            -- with inline
        do
            languages.do_all (agent  (lang: STRING)
                do
                    if lang.same_string_general ("Eiffel") then
                        print ("The OO language with DBC is :) " + lang + "%N")
                    else
                        print ("We don't know what DBC is :( " + lang + "%N")
                    end
                end)
        end

    example_do_all_with_feature
            -- with a feature
        do
            languages.do_all (agent filter_dbc)
        end

    filter_dbc (lang: STRING)
        do
            if lang.same_string_general ("Eiffel") then
                print ("The OO language with DBC is :) " + lang + "%N")
            else
                print ("We don't know what DBC is :( " + lang + "%N")
            end
        end

feature -- Access DO-IF

    example_do_if_with_inline
        do
            languages.do_if (agent  (lang: STRING)
                do
                    print ("The OO language with DBC is :) " + lang + "%N")
                end, agent  (lang: STRING): BOOLEAN
                do
                    if lang.is_case_insensitive_equal ("Eiffel") then
                        Result := True
                    end
                end)
        end

    example_do_if_with_features
        do
            languages.do_if (agent action_print, agent language_dbc_test)
        end

    action_print (a_language: STRING)
        do
            print ("The OO language with DBC is :) " + a_language + "%N")
        end

    language_dbc_test (a_language: STRING): BOOLEAN
        do
            if a_language.is_case_insensitive_equal ("Eiffel") then
                Result := True
            end
        end
end

tutorial