What are the differences in string initialization in C++? -


क्या 

  std :: string s1 ("foo") के बीच कोई अंतर है;

और 

  std :: स्ट्रिंग s2 = "foo";

?

हां और नहीं।

< P> सबसे पहले स्पष्ट रूप से आरंभ किया गया है, और दूसरा प्रतिलिपि शुरू किया गया है। मानक पहले के साथ दूसरे को बदलने की अनुमति देता है व्यवहार में, उत्पादित कोड समान होता है।

संक्षेप में ऐसा होता है: 

  std :: string s1 ("foo");

फ़ॉर्म के स्ट्रिंग कन्स्ट्रक्टर: 

  स्ट्रिंग (कॉन्स्ट char * s);

को s1 के लिए कहा जाता है।

दूसरे मामले में एक अस्थायी रूप से बनाया गया है, और उल्लेख किया गया है कि earler निर्माता उस अस्थायी के लिए कहा जाता है। उसके बाद, प्रतिलिपि निर्माता का उपयोग किया जाता है। उदा: 

  स्ट्रिंग s1 = string ("foo");

व्यवहार में, दूसरा प्रपत्र अनुकूलित है, पहले के रूप में होना चाहिए। मैंने एक कंपाइलर नहीं देखा है जो दूसरे मामले को अनुकूलित नहीं करता है।


Comments

Post a Comment

Popular posts from this blog

.net - C# List<T>.Find(x=>x.Rectangle.Contains(Point)) FAIL -

For my life, I can not understand why this code generates the following output ... I think there is a bug or something while using the list and lambda, if type one rectangle exposes the property and you use the included method of rectangle object ... and the clear statement proves true while Find list method fails .... Onway Code Public Gridskeyr Warldtokapadsb (Point location) {location = _Map.WorldToClient (location); Gridsquare gs = this.find (x => x.Rectangle.Contains (location)); GridSquare KP = G.Find (X => X. laxative canteen (location)); & Lt; GridSquare & gt; List = kp.FindAll (x => x.Rectangle.Contains (location)); U.dp (list.Count); Gridskare sub = KP.Fid (X => X. laxative canteen (location)); If (sub == faucet) {u.dp (place to look for "location"); U.dp ("The location found in the grid category" + GS toaster ()); U.dp ("Grid Square Bounds" + gs.Rectangle.ToString ()); U.dp ("location found in keypad" +...
Read more

iphone - Smoothing a rounded stroke in Core Graphics -

I am making my own UITableViewCells with a gradient background. I have worked all the logic and drawing, but the one that I want to fix is ​​"chunky" around the corners of my custom cell: If you have corners, you See what I'm talking about. Here is the code that I am using to generate cells: CGCTXT C = UigRxGroupCertexConnect (); CGColorSpaceRef myColorSpace = CGColorSpaceCreateDeviceRGB (); CGGradientRef myGradient = Zero; CGFloat component [8] = TABLE_CELL_BACKGROUND; CGContextSetStrokeColorWithColor (C, [[UAColor colorWithWhite: 0.7 alpha: 1] CGColor]); CGContextSetLineWidth (C, 2); CGContextSetAllowsAntialiasing (C, Yes); CGContextSetShouldAntialias (C, Yes); CGFloat minx = CGRectGetMinX (RECT), MIDX = CGRactgetMIDX (RECT), MAX x = CGTXxX (RECT); CGFloat miny = CGRectGetMinY (Rect), maxy = CGRectGetMaxY (rect); CGMutablePathRef Path = CGPathCreateMutable (); CGPathMoveToPoint (path, NULL, minx, miny); CGPathAddArcToPoint (default margin of path, NULL, mix, ...
Read more

c++ - QtQuick: QQmlApplicationEngine failed to load component qrc:/main.qml:23 Invalid attached object assignment -

Looking at my thoughts below, am I barking the wrong tree? Or in the information given below, am I misusing the Qt API to get an error in the title? I'm trying to modify the sample to work with the default coefficic project generated from Qt Creator 3.3.0 (OpenSource). Qt 5.4.0 (GCC 4.6.1, 64bit) Based on. The first thing to look at after the code is that I stand by: The sample uses the main.cpp: qmlRegisterType & lt ; Squircle & gt; ("OpenGLUARMM", 1, 0, "Squircle"); QQuickView view; View.setResizeMode (QQuickView :: SizeRootObjectToView); View.setSource (QUrl ("QRC: ///scenegraph/openglunderqml/main.qml")); View.show (); Some name changes in my name. CPP qmlRegisterType & lt; Menuscreen & gt; ("OpenGLUnderQML", 1, 0, "Main Screen"); QQmlApplicationEngine engine; Engine.load (QUrl (QStringLiteral ("QRC: /main.qml"))); I'm not sure that the difference in using QQmlApplicationEngine...
Read more