如何通过 gdbus 发送二维数组？答案

【问题标题】：How to send a two dimensional array over gdbus?如何通过 gdbus 发送二维数组？
【发布时间】：2017-07-07 15:27:43
【问题描述】：

我正在尝试通过 dbus 发送一个二维字符串数组。（我使用的是 gdbus api，带有 gdbus-codegen）。
我已经定义了dbus接口如下。

<method name="foo">
            <arg name="count" direction="out" type="i" />
            <arg name="array" direction="out" type="a(ia(s))" />
</method>

我正在尝试通过以下方式创建 GVariant：

GVariantBuilder *builder;
GVariant *variant;
builder = g_variant_builder_new(G_VARIANT_TYPE("a(ia(s))"));
for (int i = 0; i < count; i++)
{
    g_variant_builder_add(builder, "(ia(s))", 
                          options[i].num_supported,
                          pack_string_array(options[i].num_supported, options[i].supported_values));
}

variant = g_variant_new("a(a(s))", builder);
my_interface_complete_foo(interface, invocation, count, variant);

其中 pack_string_array 将一个 c 样式字符串数组打包到一个 gvariant 中。

GVariant* pack_string_array(int num_val, char **val)
{
    GVariantBuilder *builder;
    GVariant *values;
    builder = g_variant_builder_new(G_VARIANT_TYPE("a(s)"));
    for (int i = 0; i < num_val; i++)
    {
        g_message("%s", val[i]);
        g_variant_builder_add(builder, "(s)", val[i]);
    }

    if (num_val == 0)
        g_variant_builder_add(builder, "(s)", "NA");

    values = g_variant_new("a(s)", builder);
    return values;
}

但是当我测试它时，程序崩溃并出现以下错误：

 GLib-CRITICAL **: g_variant_builder_end: assertion 'ensure_valid_builder (builder)' failed
g_variant_get_type: assertion 'value != NULL' failed

如何通过 dbus 发送字符串数组？

【问题讨论】：

标签： arrays glib dbus gdbus gvariant

【解决方案1】：

用于构建器和变体的签名不匹配：

builder = g_variant_builder_new(G_VARIANT_TYPE("a(ia(s))"));
...
variant = g_variant_new("a(a(s))", builder);

【讨论】：

【解决方案2】：

GVariantBuilder* builder = g_variant_builder_new(G_VARIANT_TYPE("a(ia(s))"));

for (int i = 0; i < count; i++) {

    GVariantBuilder* builderStr = g_variant_builder_new(G_VARIANT_TYPE("a(s)"));
    for (int j = 0; j < nr_of_string; j++) {
        g_variant_builder_add(builderStr, "(s)", "Test");
    }
    g_variant_builder_add(builder, "(ia(s))", 32, **builderStr**);
}

GVariant* retVariant = g_variant_builder_end(builder);

【讨论】：