rust - Creating a new &str -

-

I want to map on a vector of strings so that it can be repeated to other values: 

  let's v = vec! ["Str1", "str2", "str3", "str4"] race = v.map_in_place (| x | x + "__") / error: binary operation `+` can not be applied to type ` & Amp; Str

Note that I do not need Change x , give me a New & Str by adding a new string to x . How can I do this?

Before you x to string before You can do + , like x.to_string () + "__" , but there is another problem with your code:

V type Vec & lt; & Amp; Str & gt; and map_in_place the type of type expects the size (and alignment) of the original size, and the and str size string < / Code>, so it fails in sequence -.

There are several possible changes to this task:

If you really want to use map_in_place , then you v < / Code> can be declared: 

  let's v = vec! ["Str1" .to_string (), "str2" .to_string (), "str3" .to_string (), "str4" .to_string ()];

Another way is in_iter (). The map (...) will be used. () , which will be immediately free, original vector after new creation. 

  fn main () {V = VC! ["Str1", "str2", "str3", "str4"]; Let = v.into_iter () Map (| x | x.to_string (+ + "__")) Collect: & lt; Vec & lt; _ & Gt; & Gt; (); Println! ("{}", Res); }

Output: 

  [str1__, str2__, str3__, str4__]


Comments

Post a Comment

Popular posts from this blog

mysql - How to enter php data into a html multiple select box -

-
I am working on a page that will create a team. I just want to create a selection box which will list all the users of all the users. After that, the user can select more than one friend (i.e. 5) and can send the request to these 5 people to join the team but I am having problems I did this: Select $ sql = "Select i. *, Join * Connect with M * m.id = i.clique_id where adder_id =: id"; $ Stmt = $ db- & gt; Query ($ sql, array ('id' = & gt; $ _SESSION ['id'])); While ($ record = $ stmt-> fetch ()) {$ surname = $ record ['surname']; } and this: & lt; Select multiple = "true" name = "category" well id = "category" name = "category" category = "" & gt; & Lt; Option value = "& lt ;? php echo $ surname ;? & gt;" & Gt; & Lt ;? Php ek $ nickname; ? & Gt; & Lt; / Options & gt; & Lt; / Select & gt; But only a friend's nickname...
Read more

java - Can't add JTree to JPanel of a JInternalFrame -

-
Image
There are two panels in my JInternalframe. I want to add TopPanel to Jtree to nominate another. But I can not add Jaitari to the top of the panel. Please help me in this piece of code: DefaultMutableTreeNode root = new DefaultMutableTreeNode ("deck"); DefaultMutableTreeNode Item Clubs = New DefaultMutableTreeNode ("Club"); AddAllCard (itemClubs); Root.add (itemClubs); DefaultMutableTreeNode item = New DefaultMutableTreeNode ("Diamonds"); AddAllCard (itemDiamonds); Root.add (itemDiamonds); DefaultMutableTreeNode Itemspads = New DefaultMutableTreeNode ("Spades"); AddAllCard (itemSpades); Root.add (itemSpades); DefaultMutableTreeNode item increases = new DefaultMutableTreeNode ("heart"); AddAllCard (itemHearts); Root.add (itemHearts); Default Trimodel Tree Model = New DefaultTreeModel (Route); Tree = new jetty (tree modal); ScrollPane = new JScrollPane (tree); // scrollPane.setViewportView (tree); . ScrollPane.getViewport () add (tr...
Read more

c++ - Cassandra datastax cpp driver - avoiding unnecessary copies -

-
I use the following method to create my insert statement for Cassandra (using datastax cpp driver) : ssStmt1 & lt; & Lt; "Insert some table (...) value (....)" string sStatement1 = ssStmt1.str (); Castestring cass1 = cass_string_init (sStatement1.c_str ()); CassStatement * pStmt1 = cass_statement_new (cass1, 0); I have also tried the following: CassString cass1 = cass_string_init ("Enter some table (id, date, c) value (? ,?,?); "); CassStatement * pStmt1 = cass_statement_new (cass1, 3); Cass_statement_bind_uuid (pStmt1, 0, uuidKey); Cass_statement_bind_int64 (PSTMT1, 1, timestamp); Cass_statement_bind_string (pStmt1, 2, sSomething); The first pattern works with mixed keys, the second is not. The key has a timestamp and a UUID. Timestamp is one of two errors in the field (based on the used bond statement). If bound in this way: cass_statement_bind_int64_by_name (pStmt1, "date", timestamp); I get the following error: Inva...
Read more