casting

问题 In C++ there is a way to cast a char to int and get the ascii value in return. Is there such a way to do the same with a qchar? Since unicode supports so many characters and some of them are actually looking alike, it is sometimes hard to tell what one is dealing with. An explicit code point or a number that can be used to get such would be very helpful. I searched a the web and this site for a solution but so far no luck, Qt documentation isn't much of help either, unless I'm overlooking

问题 How to do safe cast in python In c# I can safe cast by keyword as, e.g.: string word="15"; var x=word as int32// here I get 15 string word="fifteen"; var x=word as int32// here I get null Has python something similar to this? 回答1: Think not, but you may implement your own: def safe_cast(val, to_type, default=None): try: return to_type(val) except (ValueError, TypeError): return default safe_cast('tst', int) # will return None safe_cast('tst', int, 0) # will return 0 回答2: I do realize that

问题 I was looking for how to cast the interface to a struct, but I do not how I can not do it. I will try to explain my problem. type Result struct { Http_code int Http_msg string Response interface{}} This structure is returned by a function that makes an HTTP request to the server, on the other hand, I have different types of structure to wrap the response. And this is the struct which I want to cast the interface. type ResHealth struct { Type string Get_health struct { Healthy bool }} My

问题 I was looking for how to cast the interface to a struct, but I do not how I can not do it. I will try to explain my problem. type Result struct { Http_code int Http_msg string Response interface{}} This structure is returned by a function that makes an HTTP request to the server, on the other hand, I have different types of structure to wrap the response. And this is the struct which I want to cast the interface. type ResHealth struct { Type string Get_health struct { Healthy bool }} My

问题 I was looking for how to cast the interface to a struct, but I do not how I can not do it. I will try to explain my problem. type Result struct { Http_code int Http_msg string Response interface{}} This structure is returned by a function that makes an HTTP request to the server, on the other hand, I have different types of structure to wrap the response. And this is the struct which I want to cast the interface. type ResHealth struct { Type string Get_health struct { Healthy bool }} My

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I actually test the casting behavior in C# in unchecked context. Like the documentation said, in unchecked context, the cast always succeed. But sometimes, in particular cases, the cast from one specific type to another type give unexpected result. For example, i tested three "double to sbyte" casts : var firstCast = (sbyte) -129.83297462979882752; // Result : 127. var secondCast = (sbyte) -65324678217.74282742874973267; // Result : 0. var thirdCast = (sbyte) -65324678216.74282742874973267; /

问题 I have the following situation: public ArrayList<A> getMethods(){ return b.c.test(); } So, my problem is that b.c.test() returns a value with Optional<A> as return type. But I need to return an ArrayList<A> . So, I tried to cast it and rewrite it to : public ArrayList<A> getMethods(){ return (ArrayList<A>)b.c.test(); } But Eclipse says that such a cast from Optional<A> to ArrayList<A> is not possible. How can I solve this problem? 回答1: I am presuming your intended semantic is 'if the value is