显式创建类型不符合目标类型

Question

我真的不明白类型一致性的基础知识。我在 create {JANITZA_DEVICE} l_device.make_from_file_path (a_file_path) 上有一个 Creation instruction lists explicit creation type which does not conform to type of target 和 eiffel studio 19.5 enterprise。

SMA_INVERTER_MANAGER_CSV

class
    SMA_INVERTER_MANAGER_CSV

inherit
    SUNSPEC_DEVICE_CSV[SMA_INVERTER_MANAGER_DEVICE]

create
    make

SUNSPEC_DEVICE_CSV

deferred class
    SUNSPEC_DEVICE_CSV[G -> SUNSPEC_DEVICE create make_from_file_path end]

inherit
    CONSUMPTION_SECTOR_CSV[G]
        redefine
            process_file,
            set_header_csv
        end

feature --

    process_file (a_file_path: PATH)
        require else
            attached a_file_path.entry
            attached consumption_sector
        local
            l_device: like devices.item
        do
            check
                attached_consumption_sector: attached consumption_sector
            then
                if is_valid_file_path (a_file_path) then
                    if attached a_file_path.utf_8_name.has_substring ("janitza_UMG604") then
                        create {JANITZA_DEVICE} l_device.make_from_file_path (a_file_path) -- The compiler doesn't agree!
                    else
                        create l_device.make_from_file_path (a_file_path)
                    end
                    l_device.load_measuring_point (create_measuring_points, measuring_point_db_service, consumption_sector)
                    devices.extend (l_device)
                    Precursor (a_file_path) -- load measure_units from csv_row
                    devices.wipe_out
                end
            end
        ensure then
            devices.is_empty
        end

CONSUMPTION_SECTOR_CSV[G]

deferred class
    CONSUMPTION_SECTOR_CSV[G -> MEASURING_POINT_DEVICE]

feature -- Access

    devices: LINKED_SET[G]

SUNSPEC_DEVICE

class
    SUNSPEC_DEVICE

inherit
    MEASURING_POINT_DEVICE
        redefine
            default_create,
            set_measuring_point,
            out
        select
            serial
        end

    MODBUS_DEVICE
        rename
            serial as modbus_serial,
            set_serial as set_modbus_serial
        undefine
            make
        redefine
            default_create,
            make_from_file_path,
            name_from_file_path,
            out
        select
            set_modbus_serial
        end

create
    make_from_file_path

JANITZA_DEVICE

class
    JANITZA_DEVICE

inherit
    SUNSPEC_DEVICE
        redefine
            set_measure_units,
            name_from_file_path
        end

create
    make_from_file_path

Answer 1

这是一个简化的案例：

class ANIMAL

class CAT inherit ANIMAL

class HOUSE_CAT inherit CAT

class DOG inherit ANIMAL

class
    ENCLOSURE [G -> ANIMAL]
feature
    specimens: LIST [G] --> The actual type will vary with the generic parameter

    describe
        do
            print(specimens.generating_type)
        end

class
    APPLICATION

feature

    test
        local
            l_cat: CAT
            l_animal_enclosure: ENCLOSURE [ANIMAL]
            l_cat_enclosure: ENCLOSURE [CAT]
            l_house_cat_enclosure: ENCLOSURE [HOUSE_CAT]
            l_dog_enclosure: ENCLOSURE [DOG]
        do
            create l_specimen

            create l_animal_enclosure
            l_animal_enclosure.describe --> LIST [ANIMAL]
            l_animal_enclosure.specimens.add (l_cat) --> Fine, CAT conforms to ANIMAL

            create l_cat_enclosure
            l_cat_enclosure.describe --> LIST [CAT]
            l_cat_enclosure.specimens.add (l_cat) --> Fine, CAT conforms to CAT

            create l_house_cat_enclosure
            l_house_cat_enclosure.describe --> LIST [HOUSE_CAT]
            l_house_cat_enclosure.specimens.add (l_cat) --> ERROR, CAT does not conform to HOUSE_CAT


            create l_dog_enclosure
            l_dog_enclosure.describe --> LIST [DOG]
            l_dog_enclosure.specimens.add (l_cat) --> ERROR, CAT does not conform to DOG
        end

在你的例子中，devices: LINKED_SET [G] 太模糊了，没有任何证据表明 JANITZA_DEVICE 是一个有效的类型，因为 G 最终可能会在层次结构中处于较低的位置（比如 HOUSE_CAT -> CAT；您不能将 CAT 替换为 HOUSE_CAT，因此 HOUSE_CAT 的列表不能容纳 CAT) 或在单独的分支中层次结构（如 DOG -> ANIMAL；狗不是猫，它们只有一个共同的祖先）。

如果 {ENCLOSURE}.specimens 被声明为 LIST [ANIMAL] 而不是 LIST [G]，describe 将始终打印 LIST [ANIMAL] 而不管实际的泛型参数，因为类型会没有变化，因此以前的代码可以编译并且运行就好了。同样，如果 {CONSUMPTION_SECTOR_CSV}.devices 声明为 LINKED_SET [SUNSPEC_DEVICE] 而不是 LINKED_SET [G]，它可以容纳 SUNSPEC_DEVICE 的所有后代，而不管 G.[=41 的实际类型=]

或者，您可以将特定于 JANITZA_DEVICE 的部分从 CONSUMPTION_SECTOR_CSV 移动到 CONSUMPTION_SECTOR_CSV 的后代，其中 G 已关闭，如

class
    JANITZA_CONSUMPTION_SECTOR_CSV -- No generic here!
inherit
    CONSUMPTION_SECTOR_CSV [JANITZA_DEVICE]
        redefine
            process_file -- Add the parts specific to `JANITZA_DEVICE` in the implementation
        end

这将确保 devices 可以容纳实例 JANITZA_DEVICE。

Answer 2

我想user10481525已经解释了错误的原因。您的代码不保证 JANITZA_DEVICE 在 SUNSPEC_DEVICE_CSV.

的所有潜在后代中都符合 G

您已声明属性 devices: LINKED_SET [G]。因此，局部变量 l_device: like devices.item 的类型为 G。将 JANITZA_DEVICE 附加到它可能在 SUNSPEC_DEVICE_CSV 的后代中无效。为什么？因为 G 可能是 SUNSPEC_DEVICE.

的任何后代

例如，假设您有一个后代class FOO_DEVICE_CSV inherit SUNSPEC_DEVICE_CSV [FOO_DEVICE]；其中 class FOO_DEVICE inherit SUNSPEC_DEVICE。您的局部变量将有效地解析为 local l_device: FOO_DEVICE。因此，后代将尝试将类型为 JANITZA_DEVICE 的对象附加到它。但这是无效的，因为 JANITZA_DEVICE 不符合 FOO_DEVICE:

feature devices: LINKED_SET [FOO_DEVICE] ... local l_device: FOO_DEVICE ... create {JANITZA_DEVICE} l_device.make_from_file_path (a_file_path) -- Invalid!

显式创建类型不符合目标类型

explicit creation type not conforming to type of target

polymorphism

eiffel

SMA_INVERTER_MANAGER_CSV

SUNSPEC_DEVICE_CSV

CONSUMPTION_SECTOR_CSV[G]

SUNSPEC_DEVICE

JANITZA_DEVICE