问题描述
我正在寻找一种类似的方法：
myVar = try {someFunction();} catch (e) {return undefined;} ?? defaultValue;
我知道这是不正确的，但是您明白了。我只是想知道是否有一种优雅的方法？
解决方法
您目前可以做的最好的事情可能是IIFE：
final ArrayList<String> arrPackage;
String nameS = name.getText().toString().trim();
String birhtdayS = birthday.getText().toString().trim();
String gendarS = gendar.getText().toString().trim();
String phoneS = phone.getText().toString().trim();
arrPackage.add(nameS);
arrPackage.add(birhtdayS);
arrPackage.add(gendarS);
arrPackage.add(phoneS);
Gson gson = new Gson();
String json = gson.toJson(arrPackage);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString("Set",json );
editor.commit();
}
实施例如afterThrowing method modifier可能会导致表达式与OP的伪代码一样短……
DatabaseReference mMovieRef = FirebaseDatabase.getInstance().getReferenceFromUrl("xxxxxxxxxxxxxxxxxxxxxx");
mRef.child("Name");
...然后会变成类似...
const value = try {someFunction();} catch (e) {return undefined;} ?? defaultValue;
...实现和示例代码作为概念证明...
const value = (someFunction.afterThrowing(() => null)()) ?? defaultValue;
// myVar = try {someFunction();} catch (e) {return undefined;} ?? defaultValue;
function throwError() {
throw (new Error('invocation failure'));
}
function getDate() {
return Date.now();
}
const defaultValue = '... did throw.'
// expressions as short and as close as one can get
// to what has been ask for ...
//
console.log(
(getDate.afterThrowing(() => null)()) ?? defaultValue
);
console.log(
(throwError.afterThrowing(() => null)()) ?? defaultValue
);
// demonstrate capability of the after throwing handler ...
function afterThrowingHandler(error,args) {
console.log(
'afterThrowingHandler :: context,error,argsList :',this,error.toString(),Array.from(args)
);
return null; // according to the OP's use case.
}
console.log(
(getDate.afterThrowing(afterThrowingHandler)()) ?? defaultValue
);
console.log(
(throwError.afterThrowing(
afterThrowingHandler,{ biz: 'buzz' }
)('foo','bar','baz')) ?? defaultValue
);.as-console-wrapper { min-height: 100%!important; top: 0; }
我不介意有一天JavaScript正式启用... <script>
(function (Function) {
const fctPrototype = Function.prototype;
const FUNCTION_TYPE = (typeof Function);
function isFunction(type) {
return (
(typeof type == FUNCTION_TYPE)
&& (typeof type.call == FUNCTION_TYPE)
&& (typeof type.apply == FUNCTION_TYPE)
);
}
function getSanitizedTarget(target) {
return ((target != null) && target) || null;
}
function afterThrowing/*Modifier*/(handler,target) {
target = getSanitizedTarget(target);
const proceed = this;
return (
isFunction(handler) &&
isFunction(proceed) &&
function () {
const context = target || getSanitizedTarget(this);
const args = arguments;
let result;
try {
result = proceed.apply(context,args);
} catch (exception) {
result = handler.call(context,exception,args);
}
return result;
}
) || proceed;
}
// afterThrowing.toString = () => 'afterThrowing() { [native code] }';
Object.defineProperty(fctPrototype,'afterThrowing',{
configurable: true,writable: true,value: afterThrowing/*Modifier*/
});
}(Function));
</script> before Function.prototype[ after | around | afterThrowing | afterFinally |。
功能性尝试
const tryF = (func) => {
try {
return func();
} catch (e) {
return null;
}
};
然后使用
Const val = tryF(() => dosomething ())