In C++11 multi-parameter constructors can be implicitly converted to with brace initialization. However, before C++11 explicit only applied to single-argument constructors. For multiple-argument constructors, it was ignored and had no effect.
The traditional wisdom is that constructors taking one parameter (explicitly or effectively through the use of default parameters) should be marked explicit, unless they do define a conversion (std::string being convertible from const char* being one example of the latter). You’ve figured out the reasons yourself, in that implicit conversions can indeed make life harder … Read more
In C++11 multi-parameter constructors can be implicitly converted to with brace initialization. However, before C++11 explicit only applied to single-argument constructors. For multiple-argument constructors, it was ignored and had no effect.
This declares an explicit default constructor: struct A { explicit A(int a1 = 0); }; A a = 0; /* not allowed */ A b; /* allowed */ A c(0); /* allowed */ In case there is no parameter, like in the following example, the explicit is redundant. struct A { /* explicit is redundant. … Read more
Section 10.9.3 of the C# spec spells this out. The short version is that it’s disallowed so that the user can be certain that conversions between reference types and interfaces succeed if and only if the reference type actually implements that interface, and that when that conversion takes place that the same object is actually … Read more
One reason certainly is because it doesn’t hurt. One reason where it’s needed is, if you have default arguments for the first parameter. The constructor becomes a default constructor, but can still be used as converting constructor struct A { explicit A(int = 0); // added it to a default constructor }; C++0x makes actual … Read more
Reading explanation of members : explicit char_separator(const Char* dropped_delims, const Char* kept_delims = “”, empty_token_policy empty_tokens = drop_empty_tokens) explicit char_separator() The explicit keyword for the 1st constructor requires explicit creation of objects of char_separator type. What does the explicit keyword mean in C++? covers the explicit keyword very well. The explicit keyword for the 2nd … Read more
When you explicitly implement the interface, you first have to cast the object to the interface, then you can call the method. In other words, the method is only available when the method is invoked on the object as the interface type, not as the concrete type. class Vehicle: IVehicle { public int IVehicle.getWheel() { … Read more
The traditional wisdom is that constructors taking one parameter (explicitly or effectively through the use of default parameters) should be marked explicit, unless they do define a conversion (std::string being convertible from const char* being one example of the latter). You’ve figured out the reasons yourself, in that implicit conversions can indeed make life harder … Read more
This declares an explicit default constructor: struct A { explicit A(int a1 = 0); }; A a = 0; /* not allowed */ A b; /* allowed */ A c(0); /* allowed */ In case there is no parameter, like in the following example, the explicit is redundant. struct A { /* explicit is redundant. … Read more