Question

Hash1 = {
    map1: {city: 'Berlin', country: 'Germany'},
    map2: {city: 'Toronto', country: 'Canada'},
    map3: {city: 'Boston', country: 'USA' }
}

好的，所以我想构建一个如下所示的哈希：

newHash = {
    Berlin: 'map1',
    Toronto: 'map2',
    Boston: 'map3' 
}

如何循环浏览Hash1并构建newHash。

Hash1.each_with_object({}) do |(key, value), acc|
  # what do I do inside this loop?
end

Answer 1

gulp.task("uglify", ["copy-lib"],
function () {
    return gulp.src([paths.wwwroot.lib + "/jquery.js", paths.wwwroot.lib + "/bootstrap.js"])
        .pipe(sourcemaps.init())
        .pipe(concat("bundle.js"))
        .pipe(uglify())
        .pipe(isDebug, sourcemaps.write())
        .pipe(rename(addMinExtension))
        .pipe(gulp.dest(paths.wwwroot.lib));
});

Answer 2

#include <iostream>

struct A {
  int a;
  int b;
};

static A a[2]{{1, 2}, {3, 4}};

class foo {
public:
  int c;
public:
  template<typename F>
  foo(int index, F getter) { c = getter(a[index]); }
};

int main() {
  auto agetter = [](const A& a){ return a.a; };
  auto bgetter = [](const A& a){ return a.b; };

  foo const f1(0, agetter);
  std::cout << f1.c << "\n";
  foo const f2(0, bgetter);
  std::cout << f2.c << "\n";
  foo const f3(1, agetter);
  std::cout << f3.c << "\n";
  foo const f4(1, bgetter);
  std::cout << f4.c << "\n";
}

Answer 3

我只展示了以下众多方法中的一种

new_hash = Hash.new
Hash1.each do |key, value|
     new_hash[value[:city]] = key
end

Answer 4

output = {}
hash.each do |key, value|
  output[:"#{value[:city]}"] = key.to_s
end

puts output
# {:Berlin=>"map1", :Toronto=>"map2", :Boston=>"map3"}

对于确切的输出样式，您必须使用Ruby 1.9或更高版本。

使用来自另一个哈希的值构建哈希

4 个答案: