You can use btoa()
and atob()
to convert to and from base64 encoding.
There appears to be some confusion in the comments regarding what these functions accept/return, so…
btoa()
accepts a “string” where each character represents an 8-bit byte – if you pass a string containing characters that can’t be represented in 8 bits, it will probably break. This isn’t a problem if you’re actually treating the string as a byte array, but if you’re trying to do something else then you’ll have to encode it first.
atob()
returns a “string” where each character represents an 8-bit byte – that is, its value will be between 0
and 0xff
. This does not mean it’s ASCII – presumably if you’re using this function at all, you expect to be working with binary data and not text.
See also:
Most comments here are outdated. You can probably use both btoa()
and atob()
, unless you support really outdated browsers.
Check here:
The last two are identical; "atomic" is the default behavior (note that it is not actually a keyword; it is specified only by the absence of nonatomic
-- atomic
was added as a keyword in recent versions of llvm/clang).
Assuming that you are @synthesizing the method implementations, atomic vs. non-atomic changes the generated code. If you are writing your own setter/getters, atomic/nonatomic/retain/assign/copy are merely advisory. (Note: @synthesize is now the default behavior in recent versions of LLVM. There is also no need to declare instance variables; they will be synthesized automatically, too, and will have an _
prepended to their name to prevent accidental direct access).
With "atomic", the synthesized setter/getter will ensure that a whole value is always returned from the getter or set by the setter, regardless of setter activity on any other thread. That is, if thread A is in the middle of the getter while thread B calls the setter, an actual viable value -- an autoreleased object, most likely -- will be returned to the caller in A.
In nonatomic
, no such guarantees are made. Thus, nonatomic
is considerably faster than "atomic".
What "atomic" does not do is make any guarantees about thread safety. If thread A is calling the getter simultaneously with thread B and C calling the setter with different values, thread A may get any one of the three values returned -- the one prior to any setters being called or either of the values passed into the setters in B and C. Likewise, the object may end up with the value from B or C, no way to tell.
Ensuring data integrity -- one of the primary challenges of multi-threaded programming -- is achieved by other means.
Adding to this:
atomicity
of a single property also cannot guarantee thread safety when multiple dependent properties are in play.
Consider:
@property(atomic, copy) NSString *firstName;
@property(atomic, copy) NSString *lastName;
@property(readonly, atomic, copy) NSString *fullName;
In this case, thread A could be renaming the object by calling setFirstName:
and then calling setLastName:
. In the meantime, thread B may call fullName
in between thread A's two calls and will receive the new first name coupled with the old last name.
To address this, you need a transactional model. I.e. some other kind of synchronization and/or exclusion that allows one to exclude access to fullName
while the dependent properties are being updated.
Best Answer
Swift
First we need to have image's NSData
Swift 2.0 > Encoding
Swift 2.0 > Decoding
Swift 3.0 > Decoding
Encoding :
Decoding :
Swift 3.0
Objective-C
iOS7 > version
You can use
NSData's
base64EncodedStringWithOptions
Encoding :
Decoding :
iOS 6.1 and < version
First Option : Use this link to
encode
anddecode
imageAdd Base64 class in your
project
.Encoding :
Decoding :
Another Option: Use QSUtilities for
encoding
anddecoding