feat(Go-Tool)：2020/11/12:新增linq包使用示例(未完成)
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Huangzj
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package linq
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import (
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"math"
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"reflect"
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)
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// All determines whether all elements of a collection satisfy a condition.
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func (q Query) All(predicate func(interface{}) bool) bool {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if !predicate(item) {
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return false
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}
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}
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return true
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}
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// Any determines whether any element of a collection exists.
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func (q Query) Any() bool {
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_, ok := q.Iterate()()
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return ok
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}
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// AnyWith determines whether any element of a collection satisfies a condition.
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func (q Query) AnyWith(predicate func(interface{}) bool) bool {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if predicate(item) {
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return true
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}
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}
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return false
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}
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// Average computes the average of a collection of numeric values.
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func (q Query) Average() (r float64) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return math.NaN()
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}
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n := 1
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switch item.(type) {
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case int, int8, int16, int32, int64:
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conv := getIntConverter(item)
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sum := conv(item)
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for item, ok = next(); ok; item, ok = next() {
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sum += conv(item)
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n++
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}
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r = float64(sum)
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case uint, uint8, uint16, uint32, uint64:
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conv := getUIntConverter(item)
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sum := conv(item)
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for item, ok = next(); ok; item, ok = next() {
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sum += conv(item)
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n++
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}
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r = float64(sum)
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default:
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conv := getFloatConverter(item)
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r = conv(item)
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for item, ok = next(); ok; item, ok = next() {
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r += conv(item)
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n++
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}
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}
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return r / float64(n)
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}
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// Contains determines whether a collection contains a specified element.
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func (q Query) Contains(value interface{}) bool {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if item == value {
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return true
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}
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}
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return false
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}
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// Count returns the number of elements in a collection.
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func (q Query) Count() (r int) {
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next := q.Iterate()
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for _, ok := next(); ok; _, ok = next() {
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r++
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}
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return
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}
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// CountWith returns a number that represents how many elements
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// in the specified collection satisfy a condition.
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func (q Query) CountWith(predicate func(interface{}) bool) (r int) {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if predicate(item) {
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r++
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}
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}
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return
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}
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// First returns the first element of a collection.
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func (q Query) First() interface{} {
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item, _ := q.Iterate()()
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return item
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}
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// FirstWith returns the first element of a collection that satisfies
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// a specified condition.
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func (q Query) FirstWith(predicate func(interface{}) bool) interface{} {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if predicate(item) {
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return item
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}
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}
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return nil
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}
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// Last returns the last element of a collection.
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func (q Query) Last() (r interface{}) {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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r = item
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}
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return
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}
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// LastWith returns the last element of a collection that satisfies
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// a specified condition.
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func (q Query) LastWith(predicate func(interface{}) bool) (r interface{}) {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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if predicate(item) {
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r = item
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}
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}
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return
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}
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// Max returns the maximum value in a collection of values.
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func (q Query) Max() (r interface{}) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return nil
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}
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compare := getComparer(item)
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r = item
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for item, ok := next(); ok; item, ok = next() {
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if compare(item, r) > 0 {
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r = item
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}
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}
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return
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}
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// Min returns the minimum value in a collection of values.
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func (q Query) Min() (r interface{}) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return nil
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}
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compare := getComparer(item)
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r = item
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for item, ok := next(); ok; item, ok = next() {
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if compare(item, r) < 0 {
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r = item
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}
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}
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return
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}
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// Results iterates over a collection and returnes slice of interfaces
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func (q Query) Results() (r []interface{}) {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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r = append(r, item)
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}
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return
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}
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// SequenceEqual determines whether two collections are equal.
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func (q Query) SequenceEqual(q2 Query) bool {
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next := q.Iterate()
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next2 := q2.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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item2, ok2 := next2()
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if !ok2 || item != item2 {
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return false
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}
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}
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_, ok2 := next2()
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return !ok2
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}
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// Single returns the only element of a collection, and nil
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// if there is not exactly one element in the collection.
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func (q Query) Single() interface{} {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return nil
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}
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_, ok = next()
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if ok {
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return nil
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}
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return item
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}
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// SingleWith returns the only element of a collection that satisfies
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// a specified condition, and nil if more than one such element exists.
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func (q Query) SingleWith(predicate func(interface{}) bool) (r interface{}) {
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next := q.Iterate()
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found := false
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for item, ok := next(); ok; item, ok = next() {
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if predicate(item) {
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if found {
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return nil
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}
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found = true
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r = item
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}
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}
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return
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}
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// SumInts computes the sum of a collection of numeric values.
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//
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// Values can be of any integer type: int, int8, int16, int32, int64.
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// The result is int64. Method returns zero if collection contains no elements.
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func (q Query) SumInts() (r int64) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return 0
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}
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conv := getIntConverter(item)
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r = conv(item)
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for item, ok = next(); ok; item, ok = next() {
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r += conv(item)
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}
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return
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}
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// SumUInts computes the sum of a collection of numeric values.
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//
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// Values can be of any unsigned integer type: uint, uint8, uint16, uint32, uint64.
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// The result is uint64. Method returns zero if collection contains no elements.
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func (q Query) SumUInts() (r uint64) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return 0
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}
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conv := getUIntConverter(item)
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r = conv(item)
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for item, ok = next(); ok; item, ok = next() {
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r += conv(item)
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}
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return
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}
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// SumFloats computes the sum of a collection of numeric values.
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//
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// Values can be of any float type: float32 or float64. The result is float64.
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// Method returns zero if collection contains no elements.
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func (q Query) SumFloats() (r float64) {
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next := q.Iterate()
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item, ok := next()
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if !ok {
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return 0
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}
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conv := getFloatConverter(item)
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r = conv(item)
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for item, ok = next(); ok; item, ok = next() {
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r += conv(item)
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}
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return
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}
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// ToChannel iterates over a collection and outputs each element
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// to a channel, then closes it.
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func (q Query) ToChannel(result chan<- interface{}) {
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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result <- item
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}
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close(result)
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}
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// ToMap iterates over a collection and populates result map with elements.
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// Collection elements have to be of KeyValue type to use this method.
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// To populate a map with elements of different type use ToMapBy method.
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func (q Query) ToMap(result interface{}) {
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q.ToMapBy(
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result,
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func(i interface{}) interface{} {
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return i.(KeyValue).Key
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},
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func(i interface{}) interface{} {
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return i.(KeyValue).Value
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})
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}
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// ToMapBy iterates over a collection and populates result map with elements.
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// Functions keySelector and valueSelector are executed for each element of the collection
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// to generate key and value for the map. Generated key and value types must be assignable
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// to the map's key and value types.
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func (q Query) ToMapBy(
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result interface{},
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keySelector func(interface{}) interface{},
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valueSelector func(interface{}) interface{},
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) {
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res := reflect.ValueOf(result)
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m := reflect.Indirect(res)
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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key := reflect.ValueOf(keySelector(item))
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value := reflect.ValueOf(valueSelector(item))
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m.SetMapIndex(key, value)
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}
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res.Elem().Set(m)
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}
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// ToSlice iterates over a collection and populates result slice with elements.
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// Collection elements must be assignable to the slice's element type.
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func (q Query) ToSlice(result interface{}) {
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res := reflect.ValueOf(result)
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slice := reflect.Indirect(res)
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next := q.Iterate()
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for item, ok := next(); ok; item, ok = next() {
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slice = reflect.Append(slice, reflect.ValueOf(item))
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}
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res.Elem().Set(slice)
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}
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