c++ - 如何访问嵌套结构变量

Question

我有一个结构 AVFilter，

typedef struct AVFilter 
{

const char *name;  
const char *description;  
const AVClass *priv_class;  
int priv_size;  
int (*init)(AVFilterContext *ctx);  
void (*uninit)(AVFilterContext *ctx);  
int (*query_formats)(AVFilterContext *);  
const AVFilterPad *inputs;  
const AVFilterPad *outputs;  
int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);  
}  AVFilter;

我正在访问结构变量，例如，

AVFilter avfilter_vsrc_color = {  
    avfilter_vsrc_color.name            = "color",  
    avfilter_vsrc_color.description     = NULL_IF_CONFIG_SMALL("Provide an uniformly colored input."),  
    avfilter_vsrc_color.priv_class      = &color_class,        // error here  
    avfilter_vsrc_color.priv_size       = sizeof(TestSourceContext),// error here  
    avfilter_vsrc_color.init            = color_init,// error here  
    avfilter_vsrc_color.uninit          = uninit,// error here  
    avfilter_vsrc_color.query_formats   = color_query_formats,// error here  
    avfilter_vsrc_color.inputs          = NULL,// error here
    avfilter_vsrc_color.outputs         = color_outputs,// error here
    avfilter_vsrc_color.process_command = color_process_command // error here  
};

我不知道如何访问 priv_class。请帮我解决这个问题

如果我真的喜欢这样，

AVFilter avfilter_vsrc_color=
{  
    .name            = "color",  //error
    .description     = NULL_IF_CONFIG_SMALL("Provide an uniformly colored input."),  
    .priv_class      = &color_class,  
    .priv_size       = sizeof(TestSourceContext),  
    .init            = color_init,  
    .uninit          = uninit,  
    .query_formats   = color_query_formats,  
    .inputs          = NULL,  
    .outputs         = color_outputs,  
    .process_command = color_process_command  
};

我收到错误，例如，

2>c:\users\awki6\desktop\ffmpeg\libavfilter\vsrc_testsrc.cpp(271): error C2143: syntax error : missing '}' before '.'  
2>c:\users\awki6\desktop\ffmpeg\libavfilter\vsrc_testsrc.cpp(271): error C2143: syntax error : missing ';' before '.'

Answer 1

两种方式：

AVFilter avfilter_vsrc_color=
{  
     "color", 
     NULL_IF_CONFIG_SMALL("Provide an uniformly colored input."),  
     &color_class, 
     ...
};

或更冗长但也可能更具可读性（因为您有很多字段）：

AVFilter avfilter_vsrc_color;
avfilter_vsrc_color.name = color;
avfilter_vsrc_color.description = NULL_IF_CONFIG_SMALL("Provide an uniformly colored input.");
avfilter_vsrc_color.priv_class = &color_class;
...