time.Time is a struct. When you try to compare them with ==, quoting from the Spec: Comparison operator: Struct values are comparable if all their fields are comparable. Two struct values are equal if their corresponding non-blank fields are equal. So t1 == t2 will compare all the fields of the 2 Time struct values. … Read more
Edit: As the mongo-go driver evolved, it is possible to specify a projection using a simple bson.M like this: options.FindOne().SetProjection(bson.M{“_id”: 0}) Original (old) answer follows. The reason why it doesn’t work for you is because the field fields._id is unexported, and as such, no other package can access it (only the declaring package). You must … Read more
The offsetof() macro is a compile-time construct. There is no standard-compliant way to define it, but every compiler must have some way of doing it. One example would be: #define offsetof( type, member ) ( (size_t) &( ( (type *) 0 )->member ) ) While not being a compile-time construct technically (see comments by user … Read more
The problem is, as the error says, you cannot use protocols with Self or associated type requirements as actual types – as you’d lose the type information for what those requirements were. In this case, you’d lose the type information for the parameters of the == implementation – as Equatable says they must be the … Read more
Well – best practice is that structs should always (except in a few very specific scenarios, and even then at risk) be immutable. And immutable data is always thread safe. So if you followed best practice and made this: struct Data { readonly int _number; public int Number { get { return _number; } } … Read more
This looks like a perfect case for generics. You can make a single struct like this: struct ShapeRenderer<T: Shape> { canvas: Canvas, origin: Point, shape: T, } Note that I have bounded the generic type T by a trait Shape (that you would have to create). You can put any bounds here you like (or … Read more
Here are the differences between the two declarations/definitions: 1) You cannot use a typedef name to identify a constructor or a destructor struct MyStruct { MyStruct(); ~MyStruct(); }; // ok typedef struct { MyStructTD(); ~MyStructTD(); } MyStructTD; // not ok // now consider typedef struct MyStruct2 { MyStruct2(); } MyStructTD2; // ok MyStructTD2::MyStruct2() { } … Read more
One elegant way (in my opinion) of handling it is to add getters to structs that are used as pointers. This “technique” is also used by the generated Go code of protobuf, and it allows natural chaining of method calls without having to worry about runtime panic due to nil pointers. In your example the … Read more
Here’s a proof of concept: #include <stdio.h> #include <string.h> #define MEMBER(TYPE,NAME,MORE) TYPE NAME MORE #define TSTRUCT(NAME,MEMBERS) \ typedef struct NAME { \ MEMBERS \ } NAME; \ const char* const NAME##_Members = #MEMBERS; #define PRINT_STRUCT_MEMBERS(NAME) printStructMembers(NAME##_Members) TSTRUCT(S, MEMBER(int,x;, MEMBER(void*,z[2];, MEMBER(char,(*f)(char,char);, MEMBER(char,y;, ))))); void printStructMembers(const char* Members) { int level = 0; int lastLevel = 0; … Read more
The following is the decompiled ValueType.Equals method from mscorlib: public override bool Equals(object obj) { if (obj == null) { return false; } RuntimeType type = (RuntimeType) base.GetType(); RuntimeType type2 = (RuntimeType) obj.GetType(); if (type2 != type) { return false; } object a = this; if (CanCompareBits(this)) { return FastEqualsCheck(a, obj); } FieldInfo[] fields = … Read more