[String] in the picture below a cast? It feels awkward!
help me analyze why it is written this way. Is it okay not to write [String] ?
is not cast.
is an initialization with the elements in the dict.
not writing [String] is not allowed.
does not write [String]. Codes is not of type [String], but of type Dictionary < String, String > .Keys.
[String] [String]
because [String] is not written, it is a shallow copy in Swift. The memory that codes points to, or the keys of dict.
writes [String], which means that codes is re-allocated a piece of memory, and the operation against him has nothing to do with the original dict.
if Swift is not designed in this way, every time you change codes, it is copy on write. Semantically, if it is not clear, it is not safe
.the code is as follows:
let dict = ["one":"" , "two": ""]
var keys = dict.keys
var keysTwo = [String](dict.keys)
keysTwo = ["a"]
print(dict)
print(keysTwo)
this is grammar. If you don't write it, it's Any.
No, the syntax in Swift specifies what type to store when Array is created. If you haven't decided to declare it with Any or AnyObject, this is not a cast
.if you study swift carefully, you will find that it is really a rigorous language. It thinks that developers should know and be clear about the possible results. If there are omissions, it will force an error prompt. OC often leads to some unexpected results due to a lot of implicit conversions.
Previous: The problem of using cgo to develop chaincode for fabric
Next: What did the tag do after the default event was disabled to achieve the jump?
I have tried the CoreData modification operation in Demo as follows: 1, first create a new basic table and add fields, then add some data in app 2, exit app, new table, add new fields, add Relationships 3, and there is no flicker after rerunning the ...
popularize the QR code what to do when 1 out of 1 million people cannot generate a QR code? ...
when developing swift with appcode, there is no code hint after cocoapods import. But after a few days, there is inexplicable again, every project is like this, it must be a few days later, has anyone ever encountered this problem? Can it be solved? ...
what s the difference between NSStringFromClass (self) and NSStringFromClass ([self class])? ...
I want to do a macOS application, and now it s mainly stuck on the clipboard. would like to ask the gods, swift how to copy the file to the clipboard, and then right-click in the Finder to paste the file? Note: copy the file, not the text, the te...
request that many news interfaces are used. After the drop-down refresh, a prompt box comes out and studies how this is not found. Does anyone know? is the yellow box that has updated 8 pieces of information for you ...
how to compile lame3.1.0? I directly make reported that I couldn t find X841464 ....
android studio development tools how does the android camera display range consistent with the range specified by surfaceview? do not wait to display the video range beyond the range specified by surfaceview. Do not show that the video range is only di...
how do I use classification to implement lazy loading attributes in inheritance? ...
the system navigation bar is hidden on the front page according to the demand, and the navigation bar is displayed on the next page, so the problem should be very simple: the first thing that comes to mind is the inversion of ViewwillAppear: and Viewwi...
it is possible in China. But when I called American customer service, he said he couldn t open it. Has anyone ever encountered this problem 2018.05.09 know from the front end that the website server has set IP restrictions and can only be accessed...
libo info that .a spends X86-64 but reports this error when running ...
What s the use of ? ...
var table: UITableView! UITableView? Is the optional UITableView type, then UITableView! What does it mean? ...
can homebrew only install the latest version of the software? where is the source of the software, homebrew s own server? what s the difference between downloading and installing the root itself from the official website? ...
...
git remote add origin git@github.com:suiweinuv demo1.git Why remote Kujiao origin, when operating locally, but the real demo1? displayed on GitHub ...
such as svnserve-- version ...
an error is reported when using SQLite.swift to use try db.run on existing database tables (table.addColumn (title)) adds a title column. the code is as follows: create a table private func creatTable(filePath: String) { do { db = t...
seek swift advanced epub mobi e-books ...