I have this code...
NSData* myData = producedData;
NSLog(#"Contents of myData: %#", myData);
The log prints
{
"id" = "";
"level" = "level_1";
"handle" = test;
}
How do I get the values for id and level and handle out of this? The original data is a NSString*.
Thanks!
Is it JSON? Use Stig Brautaset's JSON parser http://code.google.com/p/json-framework/
You aren't showing the code that actually obtains the data object, nor are you showing any code related to an NSString.
Are you just assigning a string (producedData) to your myData variable? That won't create a data object; for one thing, it wouldn't know what encoding to use to encode the string's characters into bytes, and more importantly, copying a pointer from one variable to another (which is what myData = producedData does—the variables do not contain the objects themselves, only pointers to them) does not change anything about what the pointer points to. The object will remain a string, even though you told the compiler that myData would point to a data object. The compiler should be warning you about this; you should heed and fix those warnings.
myData definitely is not a data object; if it were, its description of itself would be a hex dump. It is either a string or a dictionary.
The output you showed matches the syntax that an NSDictionary uses to describe itself. On the other hand, the object could be a string containing such a description. (This latter case is what you're expecting.)
If you have a dictionary: You're done! The object is already parsed.
If you have a string: Send it a propertyList message, which will parse the string as a property list and return whatever value is represented in it, which, in this case, will be a dictionary.
Related
I am new to golang and I have one issue which I think community can help me to solve it.
I have one data structure like below
type ParentIDInfo struct {
PCOrderID string `json:"PCorderId",omitempty"`
TableVarieties TableVarietyDC `json:"tableVariety",omitempty"`
ProduceID string `json:"PRID",omitempty"`
}
type PCDCOrderAsset struct {
PcID string `json:"PCID",omitempty"`
DcID string `json:"DCID",omitempty"`
RequiredDate string `json:"requiredDate",omitempty"`
Qty uint64 `json:"QTY",omitempty"`
OrderID string `json:"ORDERID",omitempty"`
Status string `json:"STATUS",omitempty"`
Produce string `json:"Produce",omitempty"`
Variety string `json:"VARIETY",omitempty"`
Transports []TransportaionPCDC `json:"Transportaion",omitempty"`
ParentInfo []ParentIDInfo `json:"ParentInfo",omitempty"`
So I have issue to access the PCOrderID which inside the []ParentIDInfo . I have tried below however I getting error as "pcdcorder.ParentInfo.PCOrderID undefined (type []ParentIDInfo has no field or method PCOrderID)"
keyfarmercas = append(keyfarmercas, pcdcorder.ParentInfo.PCOrderID)
Any help will be very good
Thanks in advance
PCDCOrderAsset.ParentInfo is not a struct, it does not have a PCOrderID field. It's a slice (of element type ParentIDInfo), so its elements do, e.g. pcdcorder.ParentInfo[0].PCOrderID.
Whether this is what you want we can't tell. pcdcorder.ParentInfo[0].PCOrderID gives you the PCOrderID field of the first element of the slice. Based on your question this may or may not be what you want. You may want to append all IDs (one from each element). Also note that if the slice is empty (its length is 0), then pcdcorder.ParentInfo[0] would result in a runtime panic. You could avoid that by first checking its length and only index it if its not empty.
In case you'd want to add ids of all elements, you could use a for loop to do that, e.g.:
for i := range pcdorder.ParentInfo {
keyfarmercas = append(keyfarmercas, pcdcorder.ParentInfo[i].PCOrderID)
}
I've been looking for answers to this problem, but unfortunately without success.
I'm developing a mathematical app (Swift-based), which keeps data of every function the user enters.
(I then need to draw the functions on an NSView using a Parser)
The data structure is saved into a Dictionary but I'm not able to add values and keys.
The Dictionary is initialized like:
var functions = [String : [[String : NSBezierPath], [String : NSColor], [String : CGFloat], [String : Bool]]]();
//1A.The String key of the main Dictionary is the value of the function, such as "sin(x)"
//1B.The value of the `Dictionary` is an `Array` od `Dictionaries`
//2.The first value is a dictionary, whose key is a String and value NSBezierPath()
//3.The second value is a dictionary, whose key is a String and value NSColor()
//4.The third value is a dictionary, whose key is a String and value CGFloat()
//5.The first value is a dictionary, whose key is a String and value Bool()
To add the functions, I have implemented a method (I will report a part of) :
...
//Build the sub-dictionaries
let path : [String:NSBezierPath] = ["path" : thePath];
let color : [String:NSColor] = ["color" : theColor];
let line : [String:CGFloat] = ["lineWidth" : theLine];
let visible : [String:Bool] = ["visible" : theVisibility];
//Note that I'm 100% sure that the relative values are compatible with the relative types.
//Therefore I'm pretty sure there is a syntax error.
//Add the element (note: theFunction is a string, and I want it to be the key of the `Dictionary`)
functions[theFunction] = [path, color, line, visible]; //Error here
...
I'm given the following error:
'#|value $T10' is not identical to '(String,[([String:NSbezierPath],[String : NSColor],[String : CGFloat],[String : Bool])])'
I hope the question was enough clear and complete.
In case I will immediately add any kind of information you will need.
Best regards and happy holidays.
Dictionaries map from a specific key type to a specific value type. For example, you could make your key type String and your value type Int.
In your case, you’ve declared quite a strange dictionary: a mapping from Strings (fair enough), to an array of 4-tuples of 4 different dictionary types (each one from strings to a different type).
(It’s a new one on me, but it looks like this:
var thingy = [String,String]()
is shorthand for this:
var thingy = [(String,String)]()
Huh. Strange but it works. Your dictionary is using a variant of this trick)
This means to make your assignment work you need to create an array of a 4-tuple (note additional brackets):
functions[theFunction] = [(path, color, line, visible)]
I’m guessing you didn’t mean to do this though. Did you actually want an array of these 4 different dictionary types? If so, you’re out of luck – you can’t store different types (dictionaries that have different types for their values) in the same array.
(Well, you could if you made the values of the dictionary Any – but that’s a terrible idea and would be nightmare to use)
Probably the result you wanted was this (i.e. make the functions dictionary map from a string to a 4-tuple of dictionaries of different types):
var functions = [String : ([String : NSBezierPath], [String : NSColor], [String : CGFloat], [String : Bool])]()
You’d assign values to the dictionary like this (note, no square brackets on the rhs):
functions[theFunction] = (path, color, line, visible)
This will work but it will be pretty unpleasant to work with. But do you really want to store your structured data in dictionaries and arrays? This isn’t JavaScript ;-) You’ll tie yourself in knots navigating that multi-level dictionary. Declare a struct! It’ll be so much easier to work with in your code.
struct Functions {
var beziers: [String:NSBezierPath]
var color: [String:NSColor]
var line: [String:NSColor]
var floats: [String:CGFloat]
var bools: [String:Bool]
}
var functions: [String:Functions] = [:]
Even better, if all the beziers, colors etc are supposed to be references with the same key, declare a dictionary that contains all of them or similar.
Here's my test code:
var myDict: [String: AnyObject] = ["k":"v"]
var a = myDict["k"]
var b = a as String
var c = myDict["k"] as String
Here's my Swift playground in Xcode6-beta6:
According to the rules of type inference, doesn't complaining about c logically contradict not-complaining about b?
I believe that this is a bug. Part of what is going on here is that String is not an object. If you change the first line to:
var myDict: [String: Any] = ["k":"v"]
then everything is fine. So, given that string is not an object, casting a variable of type AnyObject? to a String should definitely yield an error. And, since the compiler has already decided that a is of type AnyObject? it should complain about casting a to a String.
Note that if you change the last line to:
var c = myDict["k"] as NSString
the error goes away supporting the notion that the issue is that String is not an object. You get the same complaint if you put an Int as the value in the array and try to cast that to an Int.
Update:
So the plot thickens. If you don't import Foundation or import something that imports Foundation, then you get additional errors. Without Foundation:
So clearly some of this has to do with the dual nature of Strings as non-objects and NSStrings as objects and the ability to use Strings as NSStrings when Foundation is imported.
This has to do with the fact that Dictionary has two subscript overloads:
subscript (key: Key) -> Value?
subscript (i: DictionaryIndex<Key, Value>) -> (Key, Value) { get }
The first is the familiar one where you pass a key and it gives you an optional of the value; and you can use to set the value on a key.
The second one is less common. I believe DictionaryIndex is a kind of iterator into the dictionary, and you can use it as a subscript to directly get the key-value pair at that iterator.
When the compiler can't find an overload that matches (in this case, the first one doesn't match because it returns an optional, which cannot be cast to non-optional String), it just picks one arbitrarily (well, it seems arbitrary to me anyway) to show in the error. In this place, it picks the second one, which you don't recognize. That's why the error seems weird to you.
This works.
var c = myDict["k"] as AnyObject! as String // "v"
To answer your question, the reason Swift complains could be that you are trying to do these two conversions in one go. Remember, the statement var a = myDict["k"] contains an implicit conversion already. The implied conversion is AnyObject?, so the above would also work like this:
var c = myDict["k"] as AnyObject? as String // "v"
Note that the above would lead to a run time error if the key "k" where not defined. You would allow this to return nil by casting to String?.
Whats the correct way in go to distinguish between when a value in a struct was never set, or is just empty, for example, given the following:
type Organisation struct {
Category string
Code string
Name string
}
I need to know (for example) if the category was never set, or was saved as blank by the user, should I be doing this:
type Organisation struct {
Category *string
Code *string
Name *string
}
I also need to ensure I correctly persist either null or an empty string to the database
I'm still learning GO so it is entirely possible my question needs more info.
The zero value for a string is an empty string, and you can't distinguish between the two.
If you are using the database/sql package, and need to distinguish between NULL and empty strings, consider using the sql.NullString type. It is a simple struct that keeps track of the NULL state:
type NullString struct {
String string
Valid bool // Valid is true if String is not NULL
}
You can scan into this type and use it as a query parameter, and the package will handle the NULL state for you.
Google's protocol buffers (https://code.google.com/p/goprotobuf/) use pointers to describe optional fields.
The generated objects provide GetFoo methods which take the pain away from testing for nil (a.GetFoo() returns an empty string if a.Foo is nil, otherwise it returns *a.Foo).
It introduces a nuisance when you want to write literal structs (in tests, for example), because &"something" is not valid syntax to generate a pointer to a string, so you need a helper function (see, for example, the source code of the protocol buffer library for proto.String).
// String is a helper routine that allocates a new string value
// to store v and returns a pointer to it.
func String(v string) *string {
return &v
}
Overall, using pointers to represent optional fields is not without drawbacks, but it's certainly a viable design choice.
The standard database/sql package provides a NullString struct (members are just String string and Valid bool). To take care of some of the repetitive work of persistence, you could look at an object-relational manager like gorp.
I looked into whether there was some way to distinguish two kinds of empty string just out of curiosity, and couldn't find one. With []bytes, []byte{} == []byte(nil) currently returns false, but I'm not sure if the spec guarantees that to always remain true. In any case, it seems like the most practical thing to do is to go with the flow and use NullString.
I have a .plist file that is loaded into my Xcode project. I have successfully put it in the documents directory of my iPhone while testing it. When I dump the contents into an NSMutableDictionary, and try to enumerate it, I get EXC_BAD_ACCESS crashes. They keys all have BOOLs associated as their values. What am I doing wrong?
My code now:
for (id key in achDict) {
NSLog(#"Achievement:%# done:%#", key, [[achDict objectForKey:key] boolValue]);
}
This always returns EXC_BAD_ACCESS in a crash.
Your NSLog is expecting two objects but you are passing it a string 'key' and an Integer. A Bool Value is not an Object, it returns an Integer value (0 for False and 1 for True). %# is for Objective C Objects. Instead use %d to get Integer Values such as C Booleans.
Change your NSLog statement to:
NSLog(#"Achievement:%# done:%d", key, [[achDict objectForKey:key] boolValue]);
Apple's String Programming Guide has a useful section on String Modifiers