chaining

问题 In javascript, Optional Chaining Operator is supported by the babel plugin. But I can't find how to do this in Typescript. Any idea? 回答1: At time of writing, TypeScript does not support the optional chaining operator. See discussion on the TypeScript issue tracker: https://github.com/Microsoft/TypeScript/issues/16 As a warning, the semantics of this operator are still very much in flux, which is why TypeScript hasn't added it yet. Code written today against the Babel plugin may change

问题 I want to do the following: pattern = cl().a().b("test").c() where cl is a class and a, b, c are class methods. After that I need to call pattern.to_string and it should output a string that was formed. Each method returns a string. Now how can I achieve the above? Append the method output to a list? What about the chainable function? If I wrote the class the normal way, the above won't work. Thank. 回答1: Return the class instance at the end of each method and store the intermediate results in

问题 I'm getting the infamous pandas SettingWithCopyWarning when I run the following code segment: for i in range(1, N): if df['deltaPressure'][i] < CLUSTER_THRESHOLD: df['Cluster'][i] = df['Cluster'][i-1] else: df['Cluster'][i] = df['Cluster'][i-1] + 1 I have tried fixing it by adding a .copy() as follows: for i in range(1, N): if df['deltaPressure'][i] < CLUSTER_THRESHOLD: df['Cluster'][i] = df['Cluster'][i-1].copy() else: df['Cluster'][i] = df['Cluster'][i-1].copy() + 1 Unfortunately, I get no

问题 I'm in the situation where I need to make 5 http calls that can be executed in parallel + another http call that need to be executed after these five. I used forkJoin for the first 5, but I don't have any idea how to chain flatMap (or other function). forkJoin( firstObservable, secondObservable, thirdObservable, ..) .subscribe(results => { this.myComposedObject = results[0]; let secondResult = results[1]; let thirdResult = results[2]; [...] // !!! AT THIS POINT I WOULD NEED TO MAKE AN EXTRA

问题 In the following code block, can someone please provide links or an explanation for the condensed alert statement syntax. I understand the preceding expanded equivalent code that is commented out and contains the message parameter. However, I cannot find a reference to the syntax for omitting the message parameter: let timeoutPromise = new Promise((resolve, reject) => { setTimeout(() => { resolve('Success!'); }, 2000); }); /* timeoutPromise.then(message => { alert(message); }) */

问题 The Java 8 coding style preferred by my colleagues is chaining asynchronous calls all the way through, e.g. CompletionStage<E> someMethod() { return doSomething().thenCompose(a -> { // ... return b; }).thenCompose(b -> { // ... return c; }).thenCompose(c -> { // ... return d; }).thenApply(d -> { // ... return e; }); } I have something like the above, but with an added challenge: I need to recall values retrieved within some of the lambdas, in later lambdas. For example, CompletionStage<E>

问题 In python, is it possible to chain together class methods and functions together? For example, if I want to instantiate a class object and call a method on it that affects an instance variable's state, could I do that? Here is an example: class Test(object): def __init__(self): self.x = 'Hello' @classmethod def make_upper(y): y.x = y.x.upper() What I'm wanting to do is this: h = Test().make_upper() I want to instantiate a class object and affect the state of a variable in one line of code,

问题 In python, is it possible to chain together class methods and functions together? For example, if I want to instantiate a class object and call a method on it that affects an instance variable's state, could I do that? Here is an example: class Test(object): def __init__(self): self.x = 'Hello' @classmethod def make_upper(y): y.x = y.x.upper() What I'm wanting to do is this: h = Test().make_upper() I want to instantiate a class object and affect the state of a variable in one line of code,

问题 Let's say we have : $("p")[0].innerHTML; and $("p").html(); In the above examples, we have the same result. So I was wondering how can JQuery return both the nodelist and itself to allow chaining ? 回答1: So I was wondering how can JQuery return both the nodelist and itself to allow chaining ? It doesn't. It only returns itself (which it an object). That object has a property called 0 which contains the first element in the array of elements. It also has a property called html which contains a

问题 I'm currently studying C# and I'm learning about constructors and the chain calling of constructors so as not to have to paste the same code (the same value for variables) in each constructor. I have three constructors, one with no parameters, one with three parameters and one with four parameters. What I'm looking to do is, use the default constructor to call the constructor with three parameters, passing default values for the parameters (variables) and the constructor that has three