Question

我试图将一个类作为参数传递给另一个类的构造函数，看起来无论我做什么，但我想出了2个错误：

'ice_type': no appropriate default constructor available

no default constructor exists for class "ice_type"

lexer.h

#pragma once
#include <string>
#include "token.h"

class ice_token;

class ice_lexer {
public:
    std::string source;
    unsigned int line;
    unsigned int pos;
    unsigned int ptr;
    ice_lexer(std::string file_name);
    ice_token lexer_next();
};

token.h

#pragma once
#include <string>
#include "lexer.h"

class ice_lexer;

enum ice_type_enum {
    ICE_NONE,
    ICE_EOF,
    ICE_MODULE,
    ICE_IDENT,
    ICE_FLT,
    ICE_NUM,
    ICE_STR,
    // SYMBOLS
    ICE_RPARA,
    ICE_LPARA,
    ICE_RBRAC,
    ICE_LBRAC,
    ICE_RCURL,
    ICE_LCURL,
    ICE_PERIOD,
    ICE_COLON,
    ICE_SEMIC,
    ICE_COMMA,
    // COMPARISON
    ICE_EQLTO,
    ICE_NOTEQL,
    ICE_GRT,
    ICE_GRTEQL,
    ICE_LES,
    ICE_LESEQL,
    // ASSIGNMENT
    ICE_EQL,
    ICE_ADDEQL,
    ICE_SUBEQL,
    ICE_MULEQL,
    ICE_DIVEQL,
    ICE_CAREQL,
    // URNARY
    ICE_URNARYNOT,
    ICE_URNARYSUB,
    // BINARY
    ICE_ADD,
    ICE_SUB,
    ICE_MUL,
    ICE_DIV,
    ICE_MOD,
    ICE_CAR,
    ICE_CAT,
    // TERNARY
    ICE_TERNARY,
    // KEYWORDS
    ICE_IMPORT,
    ICE_AS,
    ICE_WHILE,
    ICE_FOR,
    ICE_BREAK,
    ICE_IF,
    ICE_RETURN,
    ICE_TRUE,
    ICE_FALSE,
    // TYPES
    ICE_TYPEDEF,
    ICE_CLASS,
    ICE_ENUM,
    ICE_INT,
    ICE_FLOAT,
    ICE_STRING,
    ICE_BOOLEAN,
    ICE_VOID,
    ICE_STRUCT
};

static const std::string ice_type_enum_strings[] = {
    // ABSTRACT
    "no type",
    "end of file",
    "module",
    "identifier",
    "floating",
    "number",
    "string",
    // SYMBOLS
    "left para",
    "right para",
    "left brac",
    "right brac",
    "left curl",
    "right curl",
    "period",
    "colon",
    "semi",
    "comma",
    // COMPARISON
    "eql to",
    "not eql",
    "grt",
    "grt eql",
    "les",
    "les eql",
    // ASSIGNMENT
    "eql",
    "add eql",
    "sub eql",
    "mul eql",
    "div eql",
    "car eql",
    // URNARY
    "urnarynot",
    "urnarysub",
    // BINARY
    "add",
    "sub",
    "mul",
    "div",
    "mod",
    "car",
    "cat",
    // TERNARY
    "ternary",
    // KEYWORDS
    "import",
    "as",
    "while",
    "for",
    "break",
    "if",
    "return",
    "true",
    "false",
    // TYPES
    "typedef",
    "class",
    "enum",
    "int",
    "float",
    "string",
    "bool",
    "void",
    "struct"
};

class ice_type {
public:
    std::string string;
    ice_type_enum type;
    ice_type(ice_type_enum t);
};

class ice_token {
public:
    ice_type type;
    size_t line;
    size_t pos;

    union {
        std::string str;
        double flt;     
        size_t num; 
    };

    ice_token::ice_token(ice_lexer *const lexer, ice_type_enum t);
};

错误发生在ice_token的构造函数下面的文件中，visual studio intellisense将波浪形放在构造函数的开始大括号上。

#include <string>
#include "token.h"
#include "lexer.h"

ice_type::ice_type(ice_type_enum t) {
    string = ice_type_enum_strings[t];
    type = t;
}

ice_token::ice_token(ice_lexer *const lexer, ice_type_enum t) {
    type = ice_type(t);
    line = lexer->line;
    pos = lexer->pos;
    num = 0;
}

谢谢，非常感谢！

Answer 1

问题很简单。您以Java式方式初始化成员变量。但是C ++并没有这样做。构造函数总是调用所有基类的构造函数，并且成员>甚至可以调用它自己的主体。您可以使用member initializer lists为各种c指定参数。

但是你的构造函数没有，所以编译器首先尝试调用默认构造函数（没有参数一）。所以修复就是：

ice_token::ice_token(ice_lexer *const lexer, ice_type_enum t): type(t), line(lexer->line), pos(lexer->pos), num(0) {}

貌似无法将类作为构造函数参数传递

1 个答案: